Cisco Systems RJ-45-to-AUX User Manual
Table of Contents
Cisco Switching Black Book...............................................................................................................................1
Introduction.........................................................................................................................................................4
Overview..................................................................................................................................................4
Is This Book for You?..............................................................................................................................4
How to Use This Book.............................................................................................................................4
The Black Book Philosophy....................................................................................................................5
Chapter 1: Network Switching Fundamentals.................................................................................................6
In Depth...................................................................................................................................................6
Physical Media and Switching Types......................................................................................................6
A Bit of History.......................................................................................................................................7
Networking Architectures.................................................................................................................7
The Pieces of Technology........................................................................................................................9
Repeaters.........................................................................................................................................10
Hubs.................................................................................................................................................10
Bridges.............................................................................................................................................11
Routers.............................................................................................................................................13
Switches...........................................................................................................................................13
Network Design.....................................................................................................................................14
Collision Domains...........................................................................................................................15
Broadcast Domains..........................................................................................................................16
Why Upgrade to Switches?.............................................................................................................16
Switched Forwarding......................................................................................................................19
Switched Network Bottlenecks.......................................................................................................20
The Rule of the Network Road........................................................................................................22
Switched Ethernet Innovations..............................................................................................................23
Full−Duplex Ethernet......................................................................................................................23
Fast Ethernet....................................................................................................................................23
Gigabit Ethernet..............................................................................................................................24
The Cisco IOS........................................................................................................................................24
Connecting to the Switch................................................................................................................25
Powering Up the Switch..................................................................................................................25
The Challenges.......................................................................................................................................27
Today’s Trend........................................................................................................................................27
Entering and Exiting Privileged EXEC Mode.......................................................................................28
Entering and Exiting Global Configuration Mode.................................................................................28
Entering and Exiting Interface Configuration Mode.............................................................................28
Entering and Exiting Subinterface Configuration Mode.......................................................................28
Saving Configuration Changes..............................................................................................................29
Chapter 2: Basic Switch Configuration..........................................................................................................30
In Depth.................................................................................................................................................30
Command−Line Interfaces....................................................................................................................30
Campus Hierarchical Switching Model.................................................................................................31
Access Layer...................................................................................................................................32
Distribution Layer...........................................................................................................................32
Core Layer.......................................................................................................................................33
Remote Network Monitoring.................................................................................................................33
Connecting to the Console Port.............................................................................................................34
Console Cable Pinouts.....................................................................................................................35
Console Connectors.........................................................................................................................36
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Table of Contents
Chapter 2: Basic Switch Configuration
The RJ−45−to−AUX Port Console Connector Pinouts...................................................................36
Switch IOSs...........................................................................................................................................38
The IOS Configuration Modes........................................................................................................38
Limiting Telnet Access..........................................................................................................................39
Implementing Privilege Levels..............................................................................................................39
Configuring an IOS−Based CLI Switch................................................................................................39
Setting the Login Passwords...........................................................................................................40
Setting Privilege Levels...................................................................................................................40
Assigning Allowable Commands....................................................................................................40
Setting the Console Port Time−out Value.......................................................................................40
Configuring the Telnet Time−out Value.........................................................................................41
Configuring the Hostname..............................................................................................................41
Configuring the Date and Time.......................................................................................................41
Configuring an IP Address and Netmask........................................................................................41
Configuring a Default Route and Gateway.....................................................................................41
Configuring Port Speed and Duplex...............................................................................................42
Enabling SNMP Contact.................................................................................................................42
Configuring a Set/Clear−Based CLI Switch..........................................................................................42
Logging On to a Switch...................................................................................................................42
Setting the Login and Enable Passwords........................................................................................43
Changing the Console Prompt.........................................................................................................43
Entering a Contact Name and Location Information......................................................................44
Configuring System and Time Information....................................................................................44
Configuring an IP Address and Netmask........................................................................................44
Configuring a Default Route and Gateway.....................................................................................45
Viewing the Default Routes............................................................................................................45
Configuring Port Speed and Duplex...............................................................................................45
Enabling SNMP...............................................................................................................................46
Configuring Trap Message Targets.................................................................................................46
Configuring a Menu−Driven IOS..........................................................................................................47
Configuring the Console Port..........................................................................................................48
Configuring Telnet..........................................................................................................................48
Configuring the Password...............................................................................................................48
Configuring an IP Address and Default Gateway...........................................................................48
Configuring SNMP..........................................................................................................................49
Configuring ROM..................................................................................................................................50
Entering ROM Configuration Mode...............................................................................................50
Booting ROM Mode from a Flash Device......................................................................................50
Configuring SNMP..........................................................................................................................51
Configuring RMON........................................................................................................................51
Configuring RMON on a Set/Clear−Based Interface.....................................................................51
Using Set/Clear Command Set Recall Key Sequences..........................................................................52
Using IOS−Based Command Editing Keys and Functions...................................................................52
Chapter 3: WAN Switching.............................................................................................................................54
In Depth.................................................................................................................................................54
WAN Transmission Media....................................................................................................................55
Synchronous Transport Signal (STS)..............................................................................................56
Cisco WAN Switches............................................................................................................................57
MGX 8200 Series............................................................................................................................57
IGX 8400 Series..............................................................................................................................58
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Chapter 3: WAN Switching
BPX 8600 Series Wide−Area Switches..........................................................................................58
MGX 8800 Series Wide−Area Edge Switches...............................................................................59
WAN Switch Hardware Overview........................................................................................................59
Cisco WAN Switch Network Topologies..............................................................................................60
Network Management............................................................................................................................61
The CLI...........................................................................................................................................61
WAN Manager................................................................................................................................61
Accessing and Setting Up IGX and BPX Switches...............................................................................62
Adding New Users..........................................................................................................................62
Displaying a User’s Password.........................................................................................................62
Changing a User’s Password...........................................................................................................62
Using the History Command...........................................................................................................63
Displaying a Summary of All Card Modules..................................................................................63
Displaying Detailed Information for a Card Module......................................................................63
Displaying the Power and Temperature of a Switch.......................................................................63
Displaying the ASM Statistics for BPX..........................................................................................63
Configuring the ASM Setting for BPX...........................................................................................63
Logging Out....................................................................................................................................63
Resetting the Switch........................................................................................................................63
Displaying Other Switches..............................................................................................................64
Setting the Switch Name.................................................................................................................64
Setting the Time Zone.....................................................................................................................64
Configuring the Time and Date.......................................................................................................64
Configuring the Control and Auxiliary Ports..................................................................................64
Modifying the Functions of the Control and Auxiliary Ports.........................................................64
Configuring the Printing Function..................................................................................................64
Configuring the LAN Interface.......................................................................................................64
Accessing the MGX 8850 and 8220......................................................................................................65
Adding New Users..........................................................................................................................65
Changing Passwords........................................................................................................................65
Assigning a Switch Hostname.........................................................................................................65
Displaying a Summary of All Modules...........................................................................................66
Displaying Detailed Information for the Current Card...................................................................66
Changing the Time and Date...........................................................................................................66
Displaying the Configuration of the Maintenance and Control Ports.............................................66
Displaying the IP Address...............................................................................................................66
Configuring the IP Interface............................................................................................................67
Displaying the Alarm Level of the Switch......................................................................................67
Table of Contents
Chapter 4: LAN Switch Architectures............................................................................................................68
In Depth.................................................................................................................................................68
The Catalyst Crescendo Architecture....................................................................................................68
BUS.................................................................................................................................................68
ASICs..............................................................................................................................................69
The Crescendo Processors...............................................................................................................71
Crescendo Logic Units....................................................................................................................71
Other Cisco Switch Processors, Buses, ASICs, and Logic Units..........................................................72
CAM................................................................................................................................................72
AXIS Bus........................................................................................................................................72
CEF ASIC........................................................................................................................................73
Phoenix ASIC..................................................................................................................................75
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Table of Contents
Chapter 4: LAN Switch Architectures
LCP..................................................................................................................................................75
SAGE ASIC....................................................................................................................................75
QTP ASIC.......................................................................................................................................75
QMAC.............................................................................................................................................76
Bridging Types......................................................................................................................................76
Source Route Bridging....................................................................................................................76
Source Route Transparent Bridging................................................................................................77
Source Route Translational Bridging..............................................................................................77
Transparent Bridging.......................................................................................................................77
Source Route Switching..................................................................................................................77
Switching Paths......................................................................................................................................78
Process Switching............................................................................................................................78
Fast Switching.................................................................................................................................78
Autonomous Switching...................................................................................................................79
Silicon Switching............................................................................................................................79
Optimum Switching........................................................................................................................79
Distributed Switching......................................................................................................................79
NetFlow Switching..........................................................................................................................79
System Message Logging......................................................................................................................80
Loading an Image on the Supervisor Engine III....................................................................................80
Booting the Supervisor Engine III from Flash.......................................................................................81
Setting the Boot Configuration Register................................................................................................81
Configuring Cisco Express Forwarding.................................................................................................81
Enabling CEF..................................................................................................................................81
Disabling CEF.................................................................................................................................81
Enabling dCEF................................................................................................................................82
Disabling dCEF...............................................................................................................................82
Disabling CEF on an Individual Interface.......................................................................................82
Configuring CEF Load Balancing...................................................................................................82
Disabling CEF Load Balancing.......................................................................................................82
Enabling Network Accounting for CEF..........................................................................................82
Setting Network Accounting for CEF to Collect Packet Numbers.................................................82
Viewing Network Accounting for CEF Statistics...........................................................................82
Viewing CEF Packet−Dropped Statistics.......................................................................................83
Viewing Non−CEF Path Packets....................................................................................................83
Disabling Per−Destination Load Sharing..............................................................................................83
Viewing the Adjacency Table on the 8500 GSR...................................................................................83
Clearing the Adjacency Table on the 8500 GSR...................................................................................83
Enabling Console Session Logging on a Set/Clear Command−Based IOS..........................................83
Enabling Telnet Session Logging on a Set/Clear Command−Based IOS.............................................84
Disabling Console Session Logging on a Set/Clear Command−Based IOS.........................................84
Disabling Telnet Session Logging on a Set/Clear Command−Based IOS............................................84
Setting the System Message Severity Levels on a Set/Clear Command−Based IOS............................84
Enabling the Logging Time Stamp on a Set/Clear Command−Based Switch......................................84
Disabling the Logging Time Stamp on a Set/Clear Command−Based Switch.....................................85
Configuring the Logging Buffer Size on a Set/Clear Command−Based Switch...................................85
Clearing the Server Logging Table........................................................................................................85
Disabling Server Logging......................................................................................................................85
Displaying the Logging Configuration..................................................................................................86
Displaying System Logging Messages..................................................................................................86
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Table of Contents
Chapter 5: Virtual Local Area Networks.......................................................................................................88
In Depth.................................................................................................................................................88
The Flat Network of Yesterday..............................................................................................................88
Why Use VLANs?.................................................................................................................................89
VLAN Basics..................................................................................................................................90
A Properly Switched Network........................................................................................................90
Switched Internetwork Security......................................................................................................91
Scaling with VLANs..............................................................................................................................92
VLAN Boundaries...........................................................................................................................92
VLAN Membership Types..............................................................................................................93
Traffic Patterns Flowing through the Network...............................................................................93
Cisco’s VLAN Recommendations..................................................................................................93
VLAN Trunking.....................................................................................................................................94
Trunk Types....................................................................................................................................94
LAN Emulation (LANE).................................................................................................................97
VLAN Trunking Protocol (VTP)...........................................................................................................97
VTP Versions..................................................................................................................................98
VTP Advertisements.......................................................................................................................98
VTP Switch Modes.......................................................................................................................100
Methods for VLAN Identification.................................................................................................101
Dynamic Trunking Protocol..........................................................................................................101
InterVLAN Routing.............................................................................................................................101
Internal Route Processors..............................................................................................................102
How InterVLAN Routing Works..................................................................................................102
Configuring a Static VLAN on a Catalyst 5000 Series Switch...........................................................103
Configuring Multiple VLANs on a Catalyst 5000 Series Switch........................................................103
Creating VLANs on a Catalyst 1900EN Series...................................................................................103
Assigning a Static VLAN to an Interface on a 1900EN Series...........................................................104
Viewing the VLAN Configuration on a 1900 Series...........................................................................105
Viewing an Individual VLAN Configuration on a 1900 Series..........................................................105
Configuring a Trunk Port on a Cisco 5000 Series...............................................................................105
Mapping VLANs to a Trunk Port........................................................................................................107
Configuring a Trunk Port on a Cisco 1900EN Series..........................................................................107
Clearing VLANs from Trunk Links on a Cisco 5000 Series...............................................................107
Clearing VLANs from Trunk Links on a Cisco 1900EN Series.........................................................107
Verifying a Trunk Link Configuration on a 5000 Series.....................................................................108
Verifying a Trunk Link Configuration on a 1900EN Series................................................................108
Configuring the VTP Version on a Catalyst 5000 Switch...................................................................108
Configuring a VTP Domain on a Catalyst 1900 Switch......................................................................109
Setting a VTP Domain Password on a Catalyst Switch.......................................................................109
Configuring a Catalyst 1900 Switch as a VTP Server.........................................................................109
Configuring a Catalyst 1900 Switch as a VTP Client.........................................................................109
Configuring a Catalyst 1900 Switch for Transparent Mode................................................................109
Configuring VTP Pruning on a Catalyst 1900 Switch.........................................................................110
Configuring VTP on a Set/Clear CLI Switch......................................................................................110
Configuring VTP on a 1900 Cisco IOS CLI Switch...........................................................................110
Verifying the VTP Configuration on a Set/Clear CLI.........................................................................111
Displaying VTP Statistics....................................................................................................................111
Configuring VTP Pruning on a Set/Clear CLI Switch........................................................................112
Disabling Pruning for Unwanted VLANs............................................................................................112
Configuring IP InterVLAN Routing on an External Cisco Router......................................................112
Configuring IPX InterVLAN Routing on an External Router.............................................................113
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Table of Contents
Chapter 6: InterVLAN and Basic Module Configuration..........................................................................114
In Depth...............................................................................................................................................114
Internal Route Processors....................................................................................................................114
Available Route Processors...........................................................................................................116
Routing Protocol Assignment.......................................................................................................120
Supervisor Engine Modules.................................................................................................................120
Supervisor Engines I and II...........................................................................................................120
Supervisor Engine III....................................................................................................................121
Using the Supervisor Engine.........................................................................................................122
Etherport Modules...............................................................................................................................122
Port Security..................................................................................................................................123
Manually Configured MAC Addresses.........................................................................................123
Determining the Slot Number in Which a Module Resides................................................................123
Accessing the Internal Route Processor from the Switch....................................................................124
Configuring a Hostname on the RSM..................................................................................................124
Assigning an IP Address and Encapsulation Type to an Ethernet Interface........................................125
Setting the Port Speed and Port Name on an Ethernet Interface.........................................................125
Configuring a Default Gateway on a Catalyst 5000............................................................................126
Verifying the IP Configuration on a Catalyst 5000.............................................................................126
Enabling RIP on an RSM.....................................................................................................................126
Viewing the RSM’s Running Configuration.......................................................................................127
Configuring InterVLAN Routing on an RSM.....................................................................................127
Configuring IPX InterVLAN Routing on the RSM.............................................................................128
Configuring AppleTalk InterVLAN Routing on an RSM...................................................................128
Viewing the RSM Configuration.........................................................................................................129
Assigning a MAC Address to a VLAN...............................................................................................129
Viewing the MAC Addresses..............................................................................................................129
Configuring Filtering on an Ethernet Interface....................................................................................130
Configuring Port Security on an Ethernet Module..............................................................................130
Clearing MAC Addresses....................................................................................................................131
Configuring the Catalyst 5000 Supervisor Engine Module.................................................................131
Setting the boot config−register on the Supervisor Engine Module....................................................132
Changing the Management VLAN on a Supervisor Engine................................................................133
Viewing the Supervisor Engine Configuration....................................................................................133
Configuring the Cisco 2621 External Router for ISL Trunking..........................................................134
Configuring Redundancy Using HSRP...............................................................................................135
Chapter 7: IP Multicast..................................................................................................................................137
In Depth...............................................................................................................................................137
IP Multicasting Overview....................................................................................................................137
Broadcast.......................................................................................................................................138
Unicast...........................................................................................................................................138
Multicast........................................................................................................................................139
IP Multicasting Addresses...................................................................................................................140
The Multicast IP Structure............................................................................................................140
Delivery of Multicast Datagrams..................................................................................................142
Multicast Distribution Tree...........................................................................................................142
Multicast Forwarding....................................................................................................................143
IGMP Protocols.............................................................................................................................143
Internet Group Management Protocol (IGMP)....................................................................................145
IGMPv1.........................................................................................................................................145
IGMPv2.........................................................................................................................................146
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Chapter 7: IP Multicast
Time to Live..................................................................................................................................147
Multicast at Layer 2.............................................................................................................................147
IGMP Snooping.............................................................................................................................147
Cisco Group Management Protocol..............................................................................................148
Router Group Management Protocol............................................................................................148
GARP Multicast Registration Protocol.........................................................................................149
Configuring IP Multicast Routing.......................................................................................................149
Disabling IP Multicast Routing.....................................................................................................149
Enabling PIM on an Interface.......................................................................................................149
Disabling PIM on an Interface......................................................................................................149
Configuring the Rendezvous Point................................................................................................150
Adding a Router to a Multicast Group.................................................................................................150
Configuring a Router to Be a Static Multicast Group Member....................................................150
Restricting Access to a Multicast Group.......................................................................................150
Changing the IGMP Version...............................................................................................................150
Changing the IGMP Host−Query Message Interval............................................................................151
Configuring Multicast Groups.............................................................................................................151
Removing Multicast Groups................................................................................................................151
Configuring Multicast Router Ports.....................................................................................................151
Displaying Multicast Routers........................................................................................................151
Removing the Multicast Router....................................................................................................152
Configuring IGMP Snooping...............................................................................................................152
Disabling IGMP Snooping............................................................................................................152
Configuring IGMP Fast−Leave Processing.........................................................................................152
Disabling IGMP Fast−Leave Processing......................................................................................152
Displaying IGMP Statistics.................................................................................................................153
Displaying Multicast Routers Learned from IGMP.............................................................................153
Displaying IGMP Multicast Groups....................................................................................................153
Configuring CGMP..............................................................................................................................154
Disabling CGMP...........................................................................................................................154
Enabling CGMP Fast−Leave Processing......................................................................................154
Disabling CGMP Fast−Leave Processing.....................................................................................154
Displaying CGMP Statistics..........................................................................................................154
Configuring RGMP on the Switch.......................................................................................................155
Disabling RGMP on the Switch....................................................................................................155
Configuring RGMP on the Router.......................................................................................................155
Disabling RGMP on the Router....................................................................................................155
Displaying RGMP Groups...................................................................................................................155
Displaying RGMP−Capable Router Ports...........................................................................................156
Displaying RGMP VLAN Statistics....................................................................................................156
Configuring GMRP..............................................................................................................................156
Disabling GMRP...........................................................................................................................157
Enabling GMRP on Individual Ports.............................................................................................157
Disabling GMRP on Individual Ports...........................................................................................157
Enabling GMRP Forward−All......................................................................................................157
Disabling GMRP Forward−All.....................................................................................................157
Configuring GMRP Registration...................................................................................................157
Displaying the GMRP Configuration............................................................................................158
Setting GMRP Timers...................................................................................................................158
Displaying GMRP Timers.............................................................................................................158
Configuring Bandwidth−Based Suppression.......................................................................................159
Table of Contents
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Table of Contents
Chapter 7: IP Multicast
Configuring Packet−Based Suppression..............................................................................................159
Disabling Multicast Suppression.........................................................................................................159
Chapter 8: WAN Cell Switching...................................................................................................................160
In Depth...............................................................................................................................................160
ATM Overview....................................................................................................................................160
LANE............................................................................................................................................161
ATM Protocols..............................................................................................................................162
ATM Circuit Switching.................................................................................................................162
ATM Cells.....................................................................................................................................162
The ATM Switch and ATM Endpoints.........................................................................................164
The ATM Reference Model..........................................................................................................164
Specifying ATM Connections.......................................................................................................166
ATM Addressing...........................................................................................................................167
Local Area Network Emulation (LANE).............................................................................................167
LANE Components.......................................................................................................................168
Integrated Local Management Interface (ILMI)...........................................................................172
LANE Communication..................................................................................................................172
LANE Configuration Guidelines...................................................................................................174
How LANE Works........................................................................................................................174
Implementing LANE.....................................................................................................................175
Configuring ATM on the 5000 Switch..........................................................................................175
Connecting in an ATM Network...................................................................................................177
Monitoring and Maintaining LANE....................................................................................................178
Accessing the ATM LANE Module....................................................................................................178
Displaying the Selector Field...............................................................................................................178
Configuring the LES/BUS...................................................................................................................179
Verifying the LES/BUS Configuration.........................................................................................179
Configuring a LEC for an ELAN.........................................................................................................179
Verifying a LEC Configuration on an ELAN...............................................................................180
Configuring the LECS...................................................................................................................181
Viewing the LANE Database........................................................................................................181
Binding the LECS Address to an Interface...................................................................................181
Verifying the LECS Configuration...............................................................................................182
Chapter 9: LightStream Switches.................................................................................................................183
In Depth...............................................................................................................................................183
LightStream 100..................................................................................................................................183
LightStream 1010................................................................................................................................184
LightStream 2020................................................................................................................................185
Neighborhood Discovery Function...............................................................................................186
Virtual Path Connections.....................................................................................................................186
LightStream Troubleshooting Tools....................................................................................................187
LightStream Boot Process.............................................................................................................187
Supported Troubleshooting Protocols...........................................................................................188
Snooping Mechanisms..................................................................................................................188
Multiprotocol Over ATM..............................................................................................................188
Configuring the Hostname...................................................................................................................189
Configuring an Enable Password.........................................................................................................189
Configuring the Processor Card Ethernet Interface.............................................................................189
Configuring Virtual Private Tunnels...................................................................................................190
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Table of Contents
Chapter 9: LightStream Switches
Verifying an ATM Interface Connection Status..................................................................................190
Viewing the Configured Virtual Connections.....................................................................................191
Configuring the LECS ATM Address on a LightStream 1010 Switch...............................................191
Configuring the Advertised LECS Address.........................................................................................191
Viewing the LANE Configuration.......................................................................................................191
Viewing the Installed Modules............................................................................................................192
Configuring the MPC...........................................................................................................................193
Configuring the MPS...........................................................................................................................193
Changing the MPS Variables........................................................................................................193
Monitoring the MPS......................................................................................................................194
Enabling ILMI Autoconfiguration.......................................................................................................194
Configuring LANE on a LightStream 1010.........................................................................................194
Powering on the LightStream 100 ATM Switch.................................................................................195
Configuring the LS100 Switch............................................................................................................195
Recovering a Lost Password................................................................................................................196
Chapter 10: Layer 2 Redundant Links.........................................................................................................199
In Depth...............................................................................................................................................199
Layer 2 Switching Overview...............................................................................................................199
Frames..................................................................................................................................................199
Broadcast and Multicast Frames...................................................................................................200
Unknown Unicasts........................................................................................................................200
Layer 2 Network Loops.......................................................................................................................200
Danger! Data Loops!.....................................................................................................................201
Edsger Dijkstra’s Graph Theory....................................................................................................201
STP Root Bridges..........................................................................................................................202
Bridge Protocol Data Units...........................................................................................................203
Root Bridge Selection...................................................................................................................205
Spanning Tree Convergence Time................................................................................................207
STP Port States..............................................................................................................................208
Per−VLAN Spanning Tree............................................................................................................209
EtherChannel........................................................................................................................................209
Link Failure...................................................................................................................................210
Port Aggregation Protocol.............................................................................................................210
Fast Convergence Components of STP...............................................................................................211
PortFast..........................................................................................................................................211
UplinkFast.....................................................................................................................................211
BackboneFast................................................................................................................................212
Enabling STP on a Set/Clear Command−Based Switch......................................................................212
Enabling STP on a Set/Clear Command−Based Switch for All VLANs............................................213
Disabling STP on a Set/Clear Command−Based Switch.....................................................................213
Disabling STP on a Set/Clear Command−Based Switch by VLAN...................................................213
Viewing the STP Configuration on a Set/Clear Command−Based Switch.........................................213
Configuring STP on an IOS Command−Based Switch.......................................................................214
Disabling STP on an IOS Command−Based Switch...........................................................................214
Viewing the STP Configuration on a Command Line Switch.............................................................215
Configuring the STP Root Switch.......................................................................................................215
Configuring the STP Secondary Root Switch.....................................................................................215
Setting the Root Bridge for More than One VLAN on a Set/Clear Command−Based Switch...........216
Assigning a Port Cost to a Port Using the Set/Clear Command−Based IOS......................................216
Assigning a Port Cost to a Port Using a CLI−Based Switch...............................................................216
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Table of Contents
Chapter 10: Layer 2 Redundant Links
Verifying the Port Cost Configuration on Both a Set/Clear Command− and CLI−Based Interface...217
Configuring the Port Priority on a Set/Clear Command−Based IOS..................................................217
Configuring the Port Priority on a CLI−Based IOS............................................................................217
Verifying the STP Port Priority on a Set/Clear Command−Based Switch..........................................218
Verifying the VLAN Priority Settings.................................................................................................218
Adjusting the FwdDelay Timer on a Set/Clear Command−Based IOS...............................................218
Adjusting the Hello Timer on a Set/Clear Command−Based IOS......................................................218
Adjusting the MaxAge Timer on a Set/Clear Command−Based IOS.................................................219
Preparing to Enable EtherChannel.......................................................................................................219
Viewing the Port Setting for EtherChannel on a Set/Clear Command−Based Switch........................219
Creating an EtherChannel on a Set/Clear Command−Based Switch..................................................220
Verifying the EtherChannel Configuration..........................................................................................221
Defining an EtherChannel Administrative Group...............................................................................221
Viewing an EtherChannel Administrative Group................................................................................221
Configuring EtherChannel on an IOS−Based Switch..........................................................................222
Identifying the Template Port..............................................................................................................222
Verifying the EtherChannel Configuration on a Command Line Interface IOS.................................222
Enabling PortFast on a Set/Clear Command−Based Switch...............................................................223
Disabling PortFast on a Set/Clear Command−Based Switch..............................................................223
Enabling PortFast on a CLI−Based IOS Switch..................................................................................223
Disabling PortFast on a CLI−Based IOS Switch.................................................................................224
Verifying the PortFast Configuration..................................................................................................224
Enabling UplinkFast on a Set/Clear Command−Based Switch...........................................................224
Disabling UplinkFast on a Set/Clear Command−Based Switch..........................................................224
Verifying the UplinkFast Configuration..............................................................................................225
Enabling UplinkFast on a Cisco IOS Command−Based Switch.........................................................225
Disabling UplinkFast on a Cisco IOS Command−Based Switch........................................................225
Viewing the UplinkFast Configuration on an IOS−Based Switch......................................................226
Viewing UplinkFast Statistics on an IOS−Based Switch....................................................................226
Enabling BackboneFast on a Set/Clear Command−Based Switch......................................................226
Disabling BackboneFast on a Set/Clear Command−Based Switch.....................................................226
Viewing the BackboneFast Configuration...........................................................................................226
Chapter 11: Multilayer Switching.................................................................................................................227
In Depth...............................................................................................................................................227
How MLS Works.................................................................................................................................227
MLS Components..........................................................................................................................228
MLS Flows....................................................................................................................................230
Access List Flow Masks................................................................................................................231
MLS Troubleshooting Notes...............................................................................................................232
Configuring MLS.................................................................................................................................233
MLS Cache....................................................................................................................................234
Aging Timers.................................................................................................................................234
VLAN ID.......................................................................................................................................235
VTP Domain..................................................................................................................................235
Management Interfaces.................................................................................................................235
Configuring an External MLS Route Processor..................................................................................235
Enabling MLSP on an MLS−RP for IP.........................................................................................236
Disabling MLSP on an MLS−RP for IP........................................................................................236
Enabling MLSP on an MLS−RP for IPX......................................................................................236
Disabling MLSP on an MLS−RP for IPX.....................................................................................236
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Chapter 11: Multilayer Switching
Assigning a VLAN ID...................................................................................................................236
Adding an MLS Interface to a VTP Domain................................................................................236
Enabling MLS on an Individual Interface.....................................................................................237
Disabling MLS on an External Router Interface...........................................................................237
Configuring the MLS Switch Engine..................................................................................................237
Re−enabling MLS on a Catalyst 6000..........................................................................................237
Re−enabling MLS on a Catalyst 5000..........................................................................................238
Disabling MLS on a Catalyst 6000...............................................................................................238
Disabling MLS on a Catalyst 5000...............................................................................................238
Configuring the MLS Cache on the Catalyst 5000.......................................................................238
Configuring Fast Aging on a Catalyst 5000..................................................................................238
Configuring Fast Aging on a Catalyst 6000..................................................................................238
Disabling Fast Aging on a Catalyst 6000......................................................................................238
Configuring Long Aging on the Catalyst 6000.............................................................................239
Disabling Long Aging on the Catalyst 6000.................................................................................239
Configuring Normal Aging on the Catalyst 6000.........................................................................239
Disabling Normal Aging on the Catalyst 6000.............................................................................239
Assigning MLS Management to an Interface on the Catalyst 5000..............................................239
Disabling MLS Management on an Interface on the Catalyst 5000.............................................239
Monitoring and Viewing the MLS Configuration...............................................................................240
Viewing the MLS Aging Configuration on a Catalyst 6000.........................................................240
Displaying the IP MLS Configuration..........................................................................................240
Viewing MLS−RPs.......................................................................................................................240
Viewing MLS−RP Specifics.........................................................................................................240
Displaying MLS VTP Domain Information..................................................................................241
Viewing the MLS VLAN Interface Information...........................................................................241
Viewing MLS Statistics on the Catalyst 5000...............................................................................241
Viewing MLS Statistics on the Catalyst 6000...............................................................................242
Viewing MLS Entries....................................................................................................................242
Table of Contents
Chapter 12: Hot Standby Routing Protocol.................................................................................................243
In Depth...............................................................................................................................................243
Routing Problems................................................................................................................................243
Routing Information Protocol.......................................................................................................244
Proxy ARP.....................................................................................................................................244
ICMP Router Discovery Protocol.................................................................................................244
The Solution.........................................................................................................................................245
HSRP Message Format.................................................................................................................247
The HSRP States...........................................................................................................................247
HSRP Configuration............................................................................................................................248
HSRP Interface Tracking.....................................................................................................................248
Opening a Session on an Internal Route Processor.............................................................................249
Entering Configuration Mode on an RSM...........................................................................................249
Enabling HSRP and Assigning an IP Address to a Standby Group....................................................249
Assigning an HSRP Interface Priority.................................................................................................250
Assigning a Preempt Delay to a Standby Group.................................................................................250
Removing a Preempt Delay from a Standby Group............................................................................250
Setting the HSRP Hello and Hold Timers...........................................................................................250
Removing the HSRP Hello and Hold Timers......................................................................................251
Configuring a Clear−Text Password for HSRP Authentication..........................................................251
Configuring Two RSFC Interfaces as One HSRP Group....................................................................251
xi
Table of Contents
Chapter 12: Hot Standby Routing Protocol
Enabling Interface Tracking................................................................................................................252
Using the show standby Command.....................................................................................................252
Using the debug Command..................................................................................................................253
Chapter 13: Policy Networking.....................................................................................................................254
In Depth...............................................................................................................................................254
Access Security Policies......................................................................................................................254
Core Layer Policies.......................................................................................................................255
Distribution Layer Policies............................................................................................................255
Security at the Access Layer................................................................................................................261
Configuring Passwords..................................................................................................................261
Limiting Telnet Access.................................................................................................................261
Implementing Privilege Levels.....................................................................................................261
Configuring Banner Messages......................................................................................................262
Physical Device Security...............................................................................................................262
Port Security..................................................................................................................................262
VLAN Management......................................................................................................................263
Creating a Standard Access List..........................................................................................................263
Creating an Extended Access List.......................................................................................................264
Applying Access Lists Using access−class.........................................................................................266
Applying Access Lists Using distribute−list.......................................................................................266
Configuring a Telnet Session Time−Out Value..................................................................................267
Implementing Privilege Levels on a 1900EN......................................................................................267
Configuring Line Console Time−Out Values......................................................................................267
Configuring Banner Messages.............................................................................................................268
Enabling HTTP Access........................................................................................................................268
Enabling Port Security.........................................................................................................................269
Displaying the MAC Address Table....................................................................................................270
Chapter 14: Web Management......................................................................................................................272
In Depth...............................................................................................................................................272
Standard and Enterprise Edition CVSM..............................................................................................272
CVSM Client Requirements................................................................................................................272
CVSM Access Levels..........................................................................................................................273
CVSM Default Home Page..................................................................................................................273
The Switch Image..........................................................................................................................274
Configuring the Switch with an IP Address and Setting the Default Web Administration Port.........275
Connecting to the Web Management Console.....................................................................................276
Configuring the Switch Port Analyzer.................................................................................................281
Chapter 15: The Standard Edition IOS........................................................................................................283
In Depth...............................................................................................................................................283
The 1900 and 2820 Series Switches....................................................................................................283
Main Menu Choices......................................................................................................................283
[C] Console Settings......................................................................................................................284
[S] System Menu...........................................................................................................................285
[N] Network Management.............................................................................................................286
[P] Port Configuration...................................................................................................................289
[A] Port Addressing.......................................................................................................................292
[D] Port Statistics Detail................................................................................................................293
[M] Monitor...................................................................................................................................293
xii
Table of Contents
Chapter 15: The Standard Edition IOS
[V] Virtual LAN............................................................................................................................293
[R] Multicast Registration.............................................................................................................294
[F] Firmware..................................................................................................................................294
[I] RS−232 Interface......................................................................................................................295
[U] Usage Summaries...................................................................................................................296
Configuring Network Settings on the 1900 and 2820 Series...............................................................298
Configuring Broadcast Storm Control on Switch Ports.......................................................................299
Configuring SNMP on the 1900 Series...............................................................................................300
Configuring Port Monitoring on the Standard Edition IOS.................................................................303
Configuring VLANs on the Standard Edition IOS..............................................................................304
Configuring Spanning Tree Protocol...................................................................................................307
Chapter 16: Switch Troubleshooting............................................................................................................309
In Depth...............................................................................................................................................309
Hardware Troubleshooting..................................................................................................................309
No Power.......................................................................................................................................309
POST.............................................................................................................................................309
Indicator Lights.............................................................................................................................310
Switch Cabling.....................................................................................................................................311
Cable Problems..............................................................................................................................312
Cross−Over Cables........................................................................................................................312
Switch Troubleshooting Tools.............................................................................................................312
CiscoWorks for Switched Internetworks......................................................................................312
IOS Software Troubleshooting Commands..................................................................................313
Viewing the Set/Clear IOS Configuration...........................................................................................316
Viewing the CLI−Based IOS Configuration.......................................................................................320
Viewing the Software Version on a Set/Clear Command−Based IOS Module..................................321
Viewing the IOS Version Information on a CLI−Based IOS..............................................................321
Using the show flash Command on a Set/Clear Command−Based IOS.............................................321
Testing the Supervisor Engine Hardware on a Set/Clear Command−Based Switch...........................322
Testing External Module Hardware on a Set/Clear Command−Based Switch...................................323
Viewing the System Configuration on a Set/Clear Command−Based Switch....................................323
Viewing the VTP Domain Configuration on a Set/Clear IOS.............................................................324
Viewing the VTP Domain Configuration on a CLI−Based IOS.........................................................324
Viewing the VLAN Configuration on a Set/Clear Command−Based Switch.....................................324
Viewing the VLAN Configuration on a CLI−Based IOS....................................................................325
Viewing the Spanning Tree Configuration on a Set/Clear Command−Based IOS.............................325
Viewing the Spanning Tree Configuration on a CLI−Based IOS.......................................................326
Viewing the CAM (MAC Address) Table on a Set/Clear Command−Based IOS..............................328
Viewing the CAM (MAC Address) Table on a CLI−Based IOS........................................................328
Viewing the CDP Neighbors on a Set/Clear Command−Based IOS...................................................329
Viewing the CDP Neighbors on a CLI−Based IOS.............................................................................329
Viewing Individual Port CAM Tables on a CLI−Based IOS..............................................................330
Viewing Port Statistics on a Set/Clear IOS.........................................................................................330
Viewing Port Statistics on a CLI−Based IOS......................................................................................332
Using the Port Configuration on a Set/Clear Command−Based IOS..................................................333
Using the show port Command on a CLI−Based IOS.........................................................................333
Using the show vlan Command on a Set/Clear Command−Based IOS..............................................334
Using the show vlan Command on a CLI−Based IOS........................................................................334
Using the show interface Command on a Set/Clear Command−Based IOS.......................................335
Using the show interface Command on a CLI−Based IOS.................................................................335
xiii
Table of Contents
Chapter 16: Switch Troubleshooting
Using the show log Command on a Set/Clear Command−Based IOS................................................336
Configuring SPAN for Port Monitoring on a Set/Clear Command−Based IOS.................................337
Configuring SPAN for VLAN Monitoring on a Set/Clear Command−Based IOS.............................337
Launching the Diagnostic Console on a Cisco 1900 or 2820 Series Switch.......................................337
Using the Diagnostic Console to Upgrade the Firmware on a Cisco 1900 or 2820 Series Switch.....338
Using the Diagnostic Console for Debugging the Firmware and Hardware.......................................339
Appendix A: Study Resources.......................................................................................................................341
Books...................................................................................................................................................341
Cisco Group Study and Users Groups.................................................................................................341
Live Cisco Training/Internet−Based Labs/Study Resources...............................................................341
Online Resources.................................................................................................................................342
Asynchronous Transfer Mode.......................................................................................................342
Cisco IOS......................................................................................................................................342
Hot Standby Router Protocol........................................................................................................342
Inter−Switch Link.........................................................................................................................342
IP Multicast...................................................................................................................................342
Multilayer Switching.....................................................................................................................342
Quality of Service..........................................................................................................................343
Spanning Tree Protocol.................................................................................................................343
TACACS+.....................................................................................................................................343
VLANs..........................................................................................................................................343
Standards Organizations......................................................................................................................343
Cisco Job Search Sites.........................................................................................................................344
Appendix B: Basic IOS CLI−to−Set/Clear Commands..............................................................................345
Overview..............................................................................................................................................345
Appendix C: The Cisco Consultant...............................................................................................................347
Overview..............................................................................................................................................347
Establishing Credibility.......................................................................................................................347
Come Off As an Expert.................................................................................................................348
Designing a Solution............................................................................................................................348
Estimating the Cost.......................................................................................................................349
Presenting the Final Proposal and Creating Expectations.............................................................349
Contracting...........................................................................................................................................350
Document, Document, Document........................................................................................................350
The Way to Fail...................................................................................................................................350
Failing to Be There When Promised, or Rushing through the Job................................................350
Failing to Manage Your Time.......................................................................................................351
Assuming You Know What the Customer Needs.........................................................................351
Failing to Take Responsibility......................................................................................................352
Conclusion...........................................................................................................................................352
Appendix D: Cisco 1912EN and Catalyst 5000 Configuration Practice Lab............................................353
Required Equipment............................................................................................................................353
Lab Objectives.....................................................................................................................................354
Possible Solution..................................................................................................................................355
The 1912 Basic Configuration......................................................................................................355
The Catalyst 5000 Basic Configuration........................................................................................357
Configuring the Cisco 2621 Interface for ISL Trunking...............................................................358
xiv
Table of Contents
Appendix E: Switch Features........................................................................................................................359
Access Layer Switches........................................................................................................................359
Cisco Catalyst 1900.......................................................................................................................359
Cisco Catalyst 2820.......................................................................................................................360
Cisco Catalyst 2900.......................................................................................................................360
Cisco Catalyst 3000.......................................................................................................................362
Cisco Catalyst 3500 Series XL......................................................................................................362
Cisco Catalyst 3900 Series............................................................................................................363
Distribution Layer Switches................................................................................................................364
Cisco Catalyst 4000 Series............................................................................................................365
Catalyst 5000 Series......................................................................................................................365
Catalyst 6000 Series......................................................................................................................366
Core Layer/WAN Switches.................................................................................................................367
Cisco Catalyst 8400 Series............................................................................................................368
Cisco Catalyst 8500 Series............................................................................................................369
BPX 8600 Series...........................................................................................................................370
MGX 8800 Series..........................................................................................................................371
12000 Series Gigabit Switch Routers............................................................................................372
A....................................................................................................................................................373
B....................................................................................................................................................375
C....................................................................................................................................................376
D....................................................................................................................................................378
E−F................................................................................................................................................380
G−I................................................................................................................................................382
K−L...............................................................................................................................................385
M−N..............................................................................................................................................386
O−P................................................................................................................................................388
Q−R...............................................................................................................................................390
S.....................................................................................................................................................391
T.....................................................................................................................................................393
U−X...............................................................................................................................................395
xv
Cisco Switching Black Book
Sean Odom
Hanson Nottingham
© 2001 The Coriolis Group. All rights reserved.
This book may not be duplicated in any way without the express written consent of the publisher, except in
the form of brief excerpts or quotations for the purposes of review. The information contained herein is for the
personal use of the reader and may not be incorporated in any commercial programs, other books, databases,
or any kind of software without written consent of the publisher. Making copies of this book or any portion
for any purpose other than your own is a violation of United States copyright laws.
Limits of Liability and Disclaimer of Warranty
The author and publisher of this book have used their best efforts in preparing the book and the programs
contained in it. These efforts include the development, research, and testing of the theories and programs to
determine their effectiveness. The author and publisher make no warranty of any kind, expressed or implied,
with regard to these programs or the documentation contained in this book.
The author and publisher shall not be liable in the event of incidental or consequential damages in connection
with, or arising out of, the furnishing, performance, or use of the programs, associated instructions, and/or
claims of productivity gains.
Trademarks
Trademarked names appear throughout this book. Rather than list the names and entities that own the
trademarks or insert a trademark symbol with each mention of the trademarked name, the publisher states that
it is using the names for editorial purposes only and to the benefit of the trademark owner, with no intention of
infringing upon that trademark.
The Coriolis Group, LLC
14455 N. Hayden Road
Suite 220
Scottsdale, Arizona 85260
(480) 483−0192
FAX (480) 483−0193
http://www.coriolis.com/
Library of Congress Cataloging−in−Publication Data
Odom, Sean
Cisco switching black book / by Sean Odom.
p. cm.
Includes index.
ISBN 1−57610−706−X
1. Packet switching (Data transmission) I. Title.
TK5105.3 .O36 2000
004.6’6—dc21 00−064415
10 9 8 7 6 5 4 3 2 1
President and CEO
Keith Weiskamp
Publisher
1
Steve Sayre
Acquisitions Editor
Charlotte Carpentier
Product Marketing Manager
Tracy Rooney
Project Editor
Toni Zuccarini Ackley
Technical Reviewer
Deniss Suhanovs
Production Coordinator
Carla J. Schuder
Cover Designer
Jody Winkler
Layout Designer
April Nielsen
Dear Reader:
Coriolis Technology Press was founded to create a very elite group of books: the ones you keep closest to
your machine. Sure, everyone would like to have the Library of Congress at arm’s reach, but in the real world,
you have to choose the books you rely on every day very carefully.
To win a place for our books on that coveted shelf beside your PC, we guarantee several important qualities in
every book we publish. These qualities are:
•Technical accuracy—It’s no good if it doesn’t work. Every Coriolis Technology Press book is reviewed by
technical experts in the topic field, and is sent through several editing and proofreading passes in order to
create the piece of work you now hold in your hands.
•Innovative editorial design—We’ve put years of research and refinement into the ways we present
information in our books. Our books’ editorial approach is uniquely designed to reflect the way people learn
new technologies and search for solutions to technology problems.
•Practical focus—We put only pertinent information into our books and avoid any fluff. Every fact included
between these two covers must serve the mission of the book as a whole.
•Accessibility—The information in a book is worthless unless you can find it quickly when you need it. We
put a lot of effort into our indexes, and heavily cross−reference our chapters, to make it easy for you to move
right to the information you need.
Here at The Coriolis Group we have been publishing and packaging books, technical journals, and training
materials since 1989. We’re programmers and authors ourselves, and we take an ongoing active role in
defining what we publish and how we publish it. We have put a lot of thought into our books; please write to
us at ctp@coriolis.com and let us know what you think. We hope that you’re happy with the book in your
hands, and that in the future, when you reach for software development and networking information, you’ll
turn to one of our books first.
Keith Weiskamp President and CEO
2
Jeff Duntemann VP and Editorial Director
This book is dedicated to all those who endeavor to turn dreams into realities.
—Sean Odom
To my wife, Sonia, and my daughter, Sabrina.
—Hanson Nottingham
About the Authors
Sean Odom is a CCNP, MCSE, and CNX−Ethernet. He has been in the computer networking field for over
12 years and can be found instructing a number of Cisco courses, including the Switching and Remote Access
courses for Globalnet Training Solutions, Inc. (http://www.globalnettraining.com/). Sean is a former
president and currently on the board of the Sacramento Placer County Cisco Users Group (SPCCUG). In
addition, Sean has been a consultant for many companies including Advanced Computer Systems, American
Licorice, CH2M Hill, The Money Store, NCR, Wells Fargo Bank, and Intel. Sean has authored and
co−authored many industry books, labs, and white papers. You can reach Sean by email at
(sodom@rcsis.com) or see his Web site at http://www.thequestforcertification.com/.
Hanson Nottingham is a CCNA, MCSE, and MCP+I. He is an experienced Windows NT Systems Engineer
with over eight years experience in the Information Systems industry. Hanson is currently working as a
systems manager on the E:Services NT Team at Hewlett−Packard Company. Prior to HP, Hanson helped
manage Vision Service Plan’s Web farm as an Internet systems engineer. He specializes in Web farm
management and integration, SOHO network designs, and e−commerce solutions. Hanson is currently
working to further his Cisco Certified Networking Professional certification.
Acknowledgments
It’s always exciting when you get to the acknowledgments because that means the book is almost done. First
off, I must thank Erin for putting up with me during the writing of this book. She is a wonderful person who is
as smart as she is good looking and puts up with a lot of extra responsibility while I am working on books. I
also need to thank Albert Ip and Hanson Nottingham for their defined knowledge of the Cisco switches.
Thanks to my favorite English teacher, Mr. Strange, for being the one who originally thought I would be a
great writer some day, and I guess it shows here in my third book. Coriolis deserves many thanks. A few
people in particular at Coriolis need to be thanked: Steve Sayre, for believing in my idea of a Cisco Switching
Black Book; my project editor for the second time, Toni Zuccarini Ackley; Tiffany Taylor for finding all my
mistakes; Charlotte Carpentier and Shari Jo Hehr for handling the many contract issues for this book; Jody
Winkler for making the cover; Carla Schuder for making the inside of the book look good; and Paul LoPresto
for all his help in acquisitions.
—Sean Odom
Sean, thank you for giving me the opportunity and the privilege to become a co−author on this book—I
appreciate all your help, assistance, and encouragement! To my wonderful wife, Sonia, and my beautiful
daughter, Sabrina, thank you for giving me the time—dealing with my complicated and difficult schedules I
know has not been easy and your support does not go unnoticed! To Toni and the rest of the Coriolis team,
thank you for this opportunity and your undying patience throughout my process development learning
curve—I owe you guys mochas!
—Hanson Nottingham
3
Introduction
Overview
For many years I have been a consultant for different companies and have written books on switch and router
configurations and troubleshooting. During my years as a consultant I have had to either install, administer, or
troubleshoot switching problems and configurations for switches without a good handbook. I have constantly
gone through bookstores looking for a book on Cisco switch troubleshooting and configurations that didn’t
deal with a Cisco curriculum. Guess what? I couldn’t find one!
I have written books related to the CCDP and CCNP curricula and always thought about writing a book that
concentrated on Cisco switches. One day I was walking through a bookstore and noticed a book from The
Coriolis Group called Cisco Routers for IP Routing Little Black Book. I immediately thought to myself that a
Cisco Switching Little Black Book would be a great configuration handbook for many people. After contacting
Coriolis and pitching them the idea for the book, I received a call from Steve Sayre, the publisher at Coriolis,
who was excited about publishing a book of this nature. As I pondered and started putting my idea into an
outline, I realized that I could not place everything that an administrator needed in a Little Black Book.
To make a long story short, a few months later, with a great big outline and help from Albert Ip and Hanson
Nottingham, the book became this Black Book—the most feature−packed handbook for Cisco switching an
administrator can buy. Not only do we cover the Cisco Catalyst switching line but we also cover the
LightStream ATM switch series, Gigabit Switch Router Series (GSR), and the IGX and MGX WAN switch
series.
Thanks for buying the Cisco Switching Black Book.
Is This Book for You?
The Cisco Switching Black Book was written with the intermediate or advanced user in mind. Among the
topics that are covered, are:
Cisco Catalyst switch configuration and troubleshooting•
Cisco IGX and MGX switch configuration•
Cisco GSR switch configuration•
Cisco switch troubleshooting•
Cisco switch features•
ATM LightStream switch configuration and troubleshooting•
Switched network design issues•
How to Use This Book
The examples in the Immediate Solutions are intended to teach you the basic steps in configuring Cisco
Catalyst switches and their interfaces. Primarily, the Immediate Solutions will cover the information discussed
in the In Depth section of each chapter. When we explain each scenario we will use the following notations:
<Italics in angle brackets> will be used to denote command elements that have a specific value that
•
needs to be input, such as characters or numbers. Occasionally some other entry will be needed,
which will be explained in each individual instance.
[Text in square brackets] is used to denote optional commands that can be configured.•
4
Words in brackets that are separated by bars are used when indicating that there are multiple choices
•
of commands. For example, when configuring VTP you can enable the trunk port to choose one
mode: on, off, desirable, or auto mode. This will be shown like this: [on|off|desirable|auto].
Knowledge of what configuration mode you are in and how to enter each configuration mode on the Cisco
Command Line Interface is important. Knowing what each mode configures will aid you in using the proper
configuration mode. The Set/Clear command−based IOS CLI uses similar command modes as the Cisco CLI
used on Cisco routers and switches, but uses mainly the enable, set, show, and clear commands. Chapter 1
will cover the different CLI command modes.
The Black Book Philosophy
Written by experienced professionals, Coriolis Black Books provide immediate solutions to global
programming and administrative challenges, helping you complete specific tasks, especially critical ones that
are not well documented in other books. The Black Book’s unique two−part chapter format—thorough
technical overviews followed by practical immediate solutions—is structured to help you use your knowledge,
solve problems, and quickly master complex technical issues to become an expert. By breaking down
complex topics into easily manageable components, this format helps you quickly find what you’re looking
for, with commands, jump tables, and step−by−step configurations located in the Immediate Solutions section.
I welcome your feedback on this book. You can either email The Coriolis Group at ctp@coriolis.com or
email me directly at sodom@rcsis.com. Errata, updates, information on classes I teach, and more are
available at my Web site: http://www.thequestforcertification.com/.
5
Chapter 1: Network Switching Fundamentals
In Depth
Although writing the first paragraph of a book is probably the least important part, it’s invariably the most
difficult section to write. To get a good picture of the different parts of networking, readers need to know
where networking began and the history behind the networks of today. You may have seen a lot of what is in
the first section of this chapter in any basic networking course, such as Networking Essentials; or you may
have covered most of it in a CCNA class; but a refresher never hurt.
In this chapter, you will become acquainted with the history of networks and how networks evolved into those
you see in today’s corporate environments. I will also discuss the inventors of the different types of
networking equipment found at each layer of the network.
As we progress through the chapter I will also cover the different network architectures, from legacy networks
to the fast high−speed media types found in today’s networks. A clear understanding of the networking
technologies and challenges found at each layer of the network will aid you in assessing problems with the
switches you’ll deal with later.
I have a favorite quote that helps me to remember why I continuously study, so that I can better support my
customers’ equipment. It is a quote by Albert Einstein, and I remember it from one of my mentors: “The
significant [technical] problems we face cannot be solved by the same level of thinking that created them.”
This chapter will contain some of the following information:
The history of networking•
The different pieces of networking equipment•
How to identify problems in a flat network topology•
The how to’s and the when to’s of upgrading to a switched network•
When to upgrade your flat topology network•
Network upgrade planning and basic strategies•
Two terms to keep in mind when reading this chapter are resource nodes and demand nodes. A resource node
is a node on an interface attached to a device that provides resources to the network. These nodes can be
everything from printers, servers, and mainframes, to wide area network (WAN) routers. A demand node is an
interface on the network that makes requests or queries to the resource nodes. The interfaces can be devices
such as workstations, terminals, or even client applications. Network conversations occur when resource
nodes and demand nodes send a series of requests and responses through the network.
Physical Media and Switching Types
The following are the most popular types of physical media in use today:
Ethernet—Based on the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard.
•
However, it doesn’t rely on the Carrier Sense Multiple Access Collision Detection (CSMA/CD)
technology. It includes 10Mbps LANs, as well as Fast Ethernet and Gigabit Ethernet.
Token−Ring—Not as popular as Ethernet switching. Token−Ring switching can also be used to
•
improve LAN performance.
FDDI—Rarely used, chiefly due to the high expense of Fiber Distributed Data Interface (FDDI)
•
equipment and cabling.
The following are some of the protocol and physical interface switching types in use today:
6
Port switching—Takes place in the backplane of a shared hub. For instance, ports 1, 2, and 3 could be
•
connected to backplane 1, whereas ports 4, 5, and 6 could be connected to backplane 2. This method
is typically used to form a collapsed backbone and to provide some improvements in the network.
Cell switching—Uses Asynchronous Transfer Mode (ATM) as the underlying technology. Switch
•
paths can be either permanent virtual circuits (PVCs) that never go away, or switched virtual circuits
(SVCs) that are built up, used, and torn down when you’re finished.
A Bit of History
The first local area networks (LANs) began as a result of the introduction of personal computers into the
workplace environment. As computers became more common, the need arose to share resources, such as
printers or files. These early networks were pretty simple, with a handful of computers sharing a few printers
and not much more. As more items such as servers, applications, and peripherals came along, the increasing
numbers of interfaces—along with application designs that could take advantage of the network—created a
weakness in the current network design.
The limitations of traditional Ethernet technology brought forth a number of innovations that soon became
standard in the Ethernet protocol. Innovations such as full duplexing, Fast Ethernet, and Gigabit Ethernet
began to appear—innovations that have also made possible a transition to switches from shared hubs.
Other limitations to the way networks operated in a shared environment created a need for alternative methods
to permit the use of bandwidth−intensive applications such as video and voice. Switches are one of these
alternative methods. In many respects, switches are relatively simple devices. A switch’s design and
self−learning features require very little manual configuration to get it up and running. To properly use these
devices in your network, you must have an in−depth knowledge of the issues involved in implementing
switching.
Knowing the basics of Ethernet technology can help you effectively troubleshoot and install switches in the
network. You also need a good grasp of the different technologies and how switches work, as well as the
constraints of each type of device you may use in the network. As you read the following sections, make sure
you get a clear understanding of the fundamentals and basics of Ethernet technology.
The types of devices you use in the network have important implications for network performance. For
example, bridges and routers are both devices that network administrators use to extend the capabilities of
their networks. Both of them have advantages and disadvantages.
Bridges, for example, can easily solve distance limitations and increase the number of stations you can have
on a network, but they can have real problems with broadcast traffic. Routers can be used to prevent this
problem, but they increase the time it takes to forward the traffic.
This has been the pattern throughout the history of networking. When a new product is introduced, problems
or bottlenecks are soon found that limit the product’s usefulness. Then, innovations are invented or
implemented to aid the product and allow it to perform better. To see this occurrence in action, let’s take a
look at some of the traditional network architectures. As you will see in upcoming sections, the pattern of new
innovation after new innovation started in the earliest days of networking and continues in today’s networks.
Networking Architectures
Network designers from the beginnings of networking were faced with the limitations of the LAN topologies.
In modern corporate networks, LAN topologies such as Ethernet, Token Ring, and FDDI are used to provide
network connectivity. Network designers often try to deploy a design that uses the fastest functionality that
can be applied to the physical cabling.
7
Many different types of physical cable media have been introduced over the years, such as Token Ring, FDDI,
and Ethernet. At one time, Token Ring was seen as a technically superior product and a viable alternative to
Ethernet. Many networks still contain Token Ring, but very few new Token Ring installations are being
implemented. One reason is that Token Ring is an IBM product with very little support from other vendors.
Also, the prices of Token Ring networks are substantially higher than those of Ethernet networks.
FDDI networks share some of the limitations of Token Ring. Like Token Ring, FDDI offers excellent benefits
in the area of high−speed performance and redundancy. Unfortunately, however, it has the same high
equipment and installation costs. More vendors are beginning to recognize FDDI and are offering support,
services, and installation for it—especially for network backbones.
Network backbones are generally high−speed links running between segments of the network. Normally,
backbone cable links run between two routers; but they can also be found between two switches or a switch
and a router.
Ethernet has by far overwhelmed the market and obtained the highest market share. Ethernet networks are
open−standards based, more cost−effective than other types of physical media, and have a large base of
vendors that supply the different Ethernet products. The biggest benefit that makes Ethernet so popular is the
large number of technical professionals who understand how to implement and support it.
Early networks were modeled on the peer−to−peer networking model. These worked well for the small
number of nodes, but as networks grew they evolved into the client/server network model of today. Let’s take
a look at these two models in more depth.
Peer−to−Peer Networking Model
A small, flat network or LAN often contains multiple segments connected with hubs, bridges, and repeaters.
This is an Open Systems Interconnection (OSI) Reference Model Layer 2 network that can actually be
connected to a router for access to a WAN connection. In this topology, every network node sees the
conversations of every other network node.
In terms of scalability, the peer−to−peer networking model has some major limitations—especially with the
technologies that companies must utilize to stay ahead in their particular fields. No quality of service,
prioritizing of data, redundant links, or data security can be implemented here, other than encryption. Every
node sees every packet on the network. The hub merely forwards the data it receives out of every port, as
shown in Figure 1.1.
Figure 1.1: A flat network topology.
Early networks consisted of a single LAN with a number of workstations running peer−to−peer networks and
sharing files, printers, and other resources. Peer−to−peer networks share data with one another in a
non−centralized fashion and can span only a very limited area, such as a room or building.
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Client/Server Network Model
Peer−to−peer model networks evolved into the client/server model, in which the server shares applications
and data storage with the clients in a somewhat more centralized network. This setup includes a little more
security, provided by the operating system, and ease of administration for the multiple users trying to access
data.
A LAN in this environment consists of a physical wire connecting the devices. In this model, LANs enable
multiple users in a relatively small geographical area to exchange files and messages, as well as to access
shared resources such as file servers and printers. The isolation of these LANs makes communication between
different offices or departments difficult, if not impossible. Duplication of resources means that the same
hardware and software have to be supplied to each office or department, along with separate support staff for
each individual LAN.
WANs soon developed to overcome the limitations of LANs. WANs can connect LANs across normal
telephone lines or other digital media (including satellites), thereby ignoring geographical limitations in
dispersing resources to network clients.
In a traditional LAN, many limitations directly impact network users. Almost anyone who has ever used a
shared network has had to contend with the other users of that network and experienced the impacts. These
effects include such things as slow network response times, making for poor network performance. They are
due to the nature of shared environments.
When collision rates increase, the usefulness of the bandwidth decreases. As applications begin having to
resend data due to excessive collisions, the amount of bandwidth used increases and the response time for
users increases. As the number of users increases, the number of requests for network resources rises, as well.
This increase boosts the amount of traffic on the physical network media and raises the number of data
collisions in the network. This is when you begin to receive more complaints from the network’s users
regarding response times and timeouts. These are all telltale signs that you need a switched Ethernet network.
Later in this chapter, we will talk more about monitoring networks and solutions to these problems. But before
we cover how to monitor, design, and upgrade your network, let’s look at the devices you will find in the
network.
The Pieces of Technology
In 1980, a group of vendors consisting of Digital Equipment Corporation (DEC), Intel, and Xerox created
what was known as the DIX standard. Ultimately, after a few modifications, it became the IEEE 802.3
standard. It is the 802.3 standard that most people associate with the term Ethernet.
The Ethernet networking technology was invented by Robert M. Metcalfe while he was working at the Xerox
Palo Alto Research Center in the early 1970s. It was originally designed to help support research on the
“office of the future.” At first, the network’s speed was limited to 3Mbps.
Ethernet is a multiaccess, packet−switched system with very democratic principles. The stations themselves
provide access to the network, and all devices on an Ethernet LAN can access the LAN at any time. Ethernet
signals are transmitted serially, one bit at a time, over a shared channel available to every attached station.
To reduce the likelihood of multiple stations transmitting at the same time, Ethernet LANs use a mechanism
known as Carrier Sense Multiple Access Collision Detection (CSMA/CD) to listen to the network and see if it
is in use. If a station has data to transmit, and the network is not in use, the station sends the data. If two
stations transmit at the same time, a collision occurs. The stations are notified of this event, and they instantly
reschedule their transmissions using a specially designed back−off algorithm. As part of this algorithm, each
station involved chooses a random time interval to schedule the retransmission of the frame. In effect, this
process keeps the stations from making transmission attempts at the same time and prevents a collision.
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After each frame transmission, all stations on the network contend equally for the next frame transmission.
This competition allows access to the network channel in a fair manner. It also ensures that no single station
can lock out the other stations from accessing the network. Access to the shared channel is determined by the
Media Access Control (MAC) mechanism on each Network Interface Card (NIC) located in each network
node. The MAC address uses a physical address which, in terms of the OSI Reference Model, contains the
lowest level address. This is the address used by a switch. The router at Layer 3 uses a protocol address,
which is referred as a logical address.
CSMA/CD is the tool that allows collisions to be detected. Each collision of frames on the network reduces
the amount of network bandwidth that can be used to send information across the physical wire. CSMA/CD
also forces every device on the network to analyze each individual frame and determine if the device was the
intended recipient of the packet. The process of decoding and analyzing each individual packet generates
additional CPU usage on each machine, which degrades each machine’s performance.
As networks grew in popularity, they also began to grow in size and complexity. For the most part, networks
began as small isolated islands of computers. In many of the early environments, the network was installed
over a weekend—when you came in on Monday, a fat orange cable was threaded throughout the organization,
connecting all the devices. A method of connecting these segments had to be derived. In the next few sections,
we will look at a number of approaches by which networks can be connected. We will look at repeaters, hubs,
bridges, and routers, and demonstrate the benefits and drawbacks to each approach.
Repeaters
The first LANs were designed using thick coaxial cables, with each station physically tapping into the cable.
In order to extend the distance and overcome other limitations on this type of installation, a device known as a
repeater is used. Essentially, a repeater consists of a pair of back−to−back transceivers. The transmit wire on
one transceiver is hooked to the receive wire on the other, so that bits received by one transceiver are
immediately retransmitted by the other.
Repeaters work by regenerating the signals from one segment to another, and they allow networks to
overcome distance limitations and other factors. Repeaters amplify the signal to further transmit it on the
segment because there is a loss in signal energy caused by the length of the cabling. When data travels
through the physical cable it loses strength the further it travels. This loss of the signal strength is referred to
as attenuation.
These devices do not create separate networks; instead, they simply extend an existing one. A standard rule of
thumb is that no more than three repeaters may be located between any two stations. This is often referred to
as the 5−4−3 rule, which states that no more than 5 segments may be attached by no more than 4 repeaters,
with no more than 3 segments populated with workstations. This limitation prevents propagation delay, which
is the time it takes for the packet to go from the beginning of the link to the opposite end.
As you can imagine, in the early LANs this method resulted in a host of performance and fault−isolation
problems. As LANs multiplied, a more structured approach called 10BaseT was introduced. This method
consists of attaching all the devices to a hub in the wiring closet. All stations are connected in a
point−to−point configuration between the interface and the hub.
Hubs
A hub, also known as a concentrator, is a device containing a grouping of repeaters. Similar to repeaters, hubs
are found at the Physical layer of the OSI Model. These devices simply collect and retransmit bits. Hubs are
used to connect multiple cable runs in a star−wired network topology into a single network. This design is
similar to the spokes of a wheel converging on the center of the wheel.
Many benefits derive from this type of setup, such as allowing interdepartmental connections between hubs,
extending the maximum distance between any pair of nodes on the network, and improving the ability to
isolate problems from the rest of the network.
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Six types of hubs are found in the network:
Active hubs—Act as repeaters and eliminate attenuation by amplifying the signals they replicate to all
•
the attached ports.
Backbone hubs—Collect other hubs into a single collection point. This type of design is also known
•
as a multitiered design. In a typical setup, servers and other critical devices are on high−speed Fast
Ethernet or Gigabit uplinks. This setup creates a very fast connection to the servers that the
lower−speed networks can use to prevent the server or the path to the server from being a bottleneck
in the network.
Intelligent hubs—Contain logic circuits that shut down a port if the traffic indicates that malformed
•
frames are the rule rather than the exception.
Managed hubs—Have Application layer software installed so that they can be remotely managed.
•
Network management software is very popular in organizations that have staff responsible for a
network spread over multiple buildings.
Passive hubs—Aid in producing attenuation. They do not amplify the signals they replicate to all the
•
attached ports. These are the opposite of active hubs.
Stackable hubs—Have a cable to connect hubs that are in the same location without requiring the data
•
to pass through multiple hubs. This setup is commonly referred to as daisy chaining.
In all of these types of hub configurations, one crucial problem exists: All stations share the bandwidth, and
they all remain in the same collision domain. As a result, whenever two or more stations transmit
simultaneously on any hub, there is a strong likelihood that a collision will occur. These collisions lead to
congestion during high−traffic loads. As the number of stations increases, each station gets a smaller portion
of the LAN bandwidth. Hubs do not provide microsegmentation and leave only one collision domain.
Bridges
A bridge is a relatively simple device consisting of a pair of interfaces with some packet buffering and simple
logic. The bridge receives a packet on one interface, stores it in a buffer, and immediately queues it for
transmission by the other interface. The two cables each experience collisions, but collisions on one cable do
not cause collisions on the other. The cables are in separate collision domains.
Note Some bridges are capable of connecting dissimilar topologies.
The term bridging refers to a technology in which a device known as a bridge connects two or more LAN
segments. Bridges are OSI Data Link layer, or Layer 2, devices that were originally designed to connect two
network segments. Multiport bridges were introduced later to connect more than two network segments, and
they are still in use in many networks today. These devices analyze the frames as they come in and make
forwarding decisions based on information in the frames themselves.
To do its job effectively, a bridge provides three separate functions:
Filtering the frames that the bridge receives to determine if the frame should be forwarded•
Forwarding the frames that need to be forwarded to the proper interface•
Eliminating attenuation by amplifying received data signals•
Bridges learn the location of the network stations without any intervention from a network administrator or
any manual configuration of the bridge software. This process is commonly referred to as self−learning.
When a bridge is turned on and begins to operate, it examines the MAC addresses located in the headers of
frames passed through the network. As the traffic passes through the bridge, the bridge builds a table of
known source addresses, assuming the port from which the bridge received the frame is the port to which the
device is a sending device is attached.
In this table, an entry exists that contains the MAC address of each node along with the bridge interface and
port on which it resides. If the bridge knows that the destination is on the same segment as the source, it drops
the packet because there is no need to transmit it. If the bridge knows that the destination is on another
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segment, it transmits the packet on that segment or port to that segment only. If the bridge does not know the
destination segment, the bridge transmits a copy of the frame to all the interface ports in the source segment
using a technique known as flooding. For each packet an interface receives, the bridge stores in its table the
following information:
The frame’s source address•
The interface the frame arrived on•
The time at which the switch port received the source address and entered it into the switching table•
Note Bridges and switches are logically equivalent.
There are four kinds of bridges:
Transparent bridge—Primarily used in Ethernet environments. They are called transparent bridges
•
because their presence and operation are transparent to network hosts. Transparent bridges learn and
forward packets in the manner described earlier.
Source−route bridge—Primarily used in Token Ring environments. They are called source−route
•
bridges because they assume that the complete source−to−destination route is placed in frames sent
by the source.
Translational bridge—Translators between different media types, such as Token Ring and Ethernet.•
Source−route transparent bridge—A combination of transparent bridging and source−route bridging
•
that enables communication in mixed Ethernet and Token Ring environments.
Broadcasts are the biggest problem with bridges. Some bridges help reduce network traffic by filtering
packets and allowing them to be forwarded only if needed. Bridges also forward broadcasts to devices on all
segments of the network. As networks grow, so does broadcast traffic. Instead of frames being broadcast
through a limited number of devices, bridges often allow hundreds of devices on multiple segments to
broadcast data to all the devices. As a result, all devices on all segments of the network are now processing
data intended for one device. Excessive broadcasts reduce the amount of bandwidth available to end users.
This situation causes bandwidth problems called network broadcast storms. Broadcast storms occur when
broadcasts throughout the LAN use up all available bandwidth, thus grinding the network to a halt.
Network performance is most often affected by three types of broadcast traffic: inquiries about the availability
of a device, advertisements for a component’s status on the network, and inquiries from one device trying to
locate another device. The following are the typical types of network broadcasts:
Address Resolution Protocol (ARP)•
Internetwork Packet Exchange (IPX) Get Nearest Server (GNS) requests•
IPX Service Advertising Protocol (SAP)•
Multicast traffic broadcasts•
NetBIOS name requests•
These broadcasts are built into the network protocols and are essential to the operation of the network devices
using these protocols.
Due to the overhead involved in forwarding packets, bridges also introduce a delay in forwarding traffic. This
delay is known as latency. Latency delay is measured from the moment a packet enters the input port on the
switch until the time the bridge forwards the packet out the exit port. Bridges can introduce 20 to 30 percent
loss of throughput for some applications. Latency is a big problem with some timing−dependent technologies,
such as mainframe connectivity, video, or voice.
High levels of latency can result in loss of connections and noticeable video and voice degradation. The
inherent problems of bridging over multiple segments including those of different LAN types with Layer 2
devices became a problem to network administrators. To overcome these issues, a device called a router,
operating at OSI Layer 3, was introduced.
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Routers
Routers are devices that operate at Layer 3 of the OSI Model. Routers can be used to connect more than one
Ethernet segment with or without bridging. Routers perform the same basic functions as bridges and also
forward information and filter broadcasts between multiple segments. Figure 1.2 shows routers segmenting
multiple network segments. Using an OSI network Layer 3 solution, routers logically segment traffic into
subnets.
Figure 1.2: Routers connecting multiple segments.
Routers were originally introduced to connect dissimilar network media types as well as to provide a means to
route traffic, filter broadcasts across multiple segments, and improve overall performance. This approach
eliminated broadcasts over multiple segments by filtering broadcasts. However, routers became a bottleneck
in some networks and also resulted in a loss of throughput for some types of traffic.
When you are connecting large networks, or when you are connecting networks to a WAN, routers are very
important. Routers will perform media conversion, adjusting the data link protocol as necessary. With a
router, as well as with some bridges, you can connect an Ethernet network and a Token Ring network.
Routers do have some disadvantages. The cost of routers is very high, so they are an expensive way to
segment networks. If protocol routing is necessary, you must pay this cost. Routers are also difficult to
configure and maintain, meaning that you will have a difficult time keeping the network up and running.
Knowledgeable workers who understand routing can be expensive.
Routers are also somewhat limited in their performance, especially in the areas of latency and forwarding
rates. Routers add about 40 percent additional latency from the time packets arrive at the router to the time
they exit the router. Higher latency is primarily due to the fact that routing requires more packet assembly and
disassembly. These disadvantages force network administrators to look elsewhere when designing many large
network installations.
Switches
A new option had to be developed to overcome the problems associated with bridges and routers. These new
devices were called switches. The term switching was originally applied to packet−switch technologies, such
as Link Access Procedure, Balanced (LAPB); Frame Relay; Switched Multimegabit Data Service (SMDS);
and X.25. Today, switching is more commonly associated with LAN switching and refers to a technology that
is similar to a bridge in many ways.
Switches allow fast data transfers without introducing the latency typically associated with bridging. They
create a one−to−one dedicated network segment for each device on the network and interconnect these
segments by using an extremely fast, high−capacity infrastructure that provides optimal transport of data on a
LAN; this structure is commonly referred to as a backplane. This setup reduces competition for bandwidth on
the network, allows maximum utilization of the network, and increases flexibility for network designers and
implementers.
Ethernet switches provide a number of enhancements over shared networks. Among the most important is
microsegmentation, which is the ability to divide networks into smaller and faster segments that can operate at
the maximum possible speed of the wire (also known as wire−speed).
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To improving network performance, switches must address three issues:
They must stop unneeded traffic from crossing network segments.•
They must allow multiple communication paths between segments.•
They cannot introduce performance degradation.•
Routers are also used to improve performance. Routers are typically attached to switches to connect multiple
LAN segments. A switch forwards the traffic to the port on the switch to which the destination device is
connected, which in turn reduces the traffic to the other devices on the network. Information from the sending
device is routed directly to the receiving device. No device other than the router, switch, and end nodes sees or
processes the information.
The network now becomes less saturated, more secure, and more efficient at processing information, and
precious processor time is freed on the local devices. Routers today are typically placed at the edge of the
network and are used to connect WANs, filter traffic, and provide security. See Figure 1.3.
Figure 1.3: Routers and switches
Like bridges, switches perform at OSI Layer 2 by examining the packets and building a forwarding table
based on what they hear. Switches differ from bridges by helping to meet the following needs for network
designers and administrators:
Provide deterministic paths•
Relieve network bottlenecks•
Provide deterministic failover for redundancy•
Allow scalable network growth•
Provide fast convergence•
Act as a means to centralize applications and servers•
Have the capacity to reduce latency•
Network Design
When designing or upgrading your network, you need to keep some basic rules of segmenting in mind. You
segment your network primarily to relieve network congestion and route data as quickly and efficiently as
possible. Segmentation is often necessary to satisfy the bandwidth requirements of a new application or type
of information that the network needs to support. Other times, it may be needed due to the increased traffic on
the segment or subnet. You should also plan for increased levels of network usage or unplanned increases in
network population.
Some areas you need to consider are the types of nodes, user groups, security needs, population of the
network, applications used, and the network needs for all the interfaces on the network. When designing your
network, you should create it in a hierarchical manner. Doing so provides you with the ability to easily make
additions to your network. Another important consideration should be how your data flows through the
network.
For example, let’s say your users are intermingled with your servers in the same geographical location. If you
create a switched network in which the users’ data must be switched through a number of links to another
geographical area and then back again to create a connection between the users and file servers, you have not
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