3COM CS 2500 User Manual
LAN
®
S
WITCHING
PLEX
®
2500 E
U
SER
XTENDED
G
UIDE
Part No. 801-00343-000
Published November 1996
Revision 02
3Com Corporation
5400 Bayfront Plaza
■
Santa Clara, California
■
95052-8145
■
© 3Com Corporation, 1996. All rights reserved. No part of this documentation may be reproduced in any form or by any means or used to make
any derivative work (such as translation, transformation, or adaptation) without permission from 3Com Corporation.
3Com Corporation reserves the right to revise this documentation and to make changes in content from time to time without obligation on the
part of 3Com Corporation to provide notification of such revision or change.
3Com Corporation provides this documentation without warranty of any kind, either implied or expressed, including, but not limited to, the
implied warranties of merchantability and fitness for a particular purpose. 3Com may make improvements or changes in the product(s) and/or
the program(s) described in this documentation at any time.
UNITED STATES GOVERNMENT LEGENDS:
If you are a United States government agency, then this documentation and the software described herein are provided to you subject to the
following restricted rights:
For units of the Department of Defense:
Restricted Rights Legend: Use, duplication or disclosure by the Government is subject to restrictions as set forth in subparagraph (c) (1) (ii) for
restricted Rights in Technical Data and Computer Software clause at 48 C.F.R. 52.227-7013. 3Com Corporation, 5400 Bayfront Plaza, Santa Clara,
California 95052-8145.
For civilian agencies:
Restricted Rights Legend: Use, reproduction or disclosure is subject to restrictions set forth in subparagraph (a) through (d) of the Commercial
Computer Software - Restricted Rights Clause at 48 C.F.R. 52.227-19 and the limitations set forth in 3Com’s standard commercial agreement for
the software. Unpublished rights reserved under the copyright laws of the United States.
3ComFacts, Ask3Com, CardFacts, NetFacts, and CardBoard are service marks of 3Com Corporation.
3Com, LANplex, Transcend, and NETBuilder II are registered trademarks of 3Com Corporation.
CompuServe is a registered trademark of CompuServe, Inc.
3Com registered trademarks are registered in the United States, and may or may not be registered in other countries.
Other brand and product names may be registered trademarks or trademarks of their respective holders.
Guide written, edited, and illustrated by Trish Crawford, Lynne Gelfand, Michael Jenness, Dave Sullivan, Patricia Johnson, Michael Taillon, Iain
Young, and Bonnie Jo Collins.
C
ONTENTS
A
BOUT
T
HIS
G
UIDE
Introduction 1
How to Use This Guide 1
Conventions 2
LANplex 2500 Documentation 3
Documentation Comments 5
P
P
ART
ART
IG
1
II V
2
ETTING
LAN
About LANplex Extended Switching 1-1
Using Menus 1-2
IRTUAL
VLAN
About VLANs 2-1
S
TARTED
PLEX
® E
XTENDED
Bridge Menu 1-3
IP Menu 1-4
IPX Menu 1-5
Appletalk Menu 1-6
LAN T
S
ON
THE
LAN
Types of VLANs 2-1
Port Group VLANs 2-1
MAC Address Group VLANS 2-2
Application-Oriented VLANS 2-2
Protocol-Sensitive VLANS 2-2
LANplex Protocol-Sensitive VLAN Configuration 2-3
Protocol Suite 2-3
Switch Ports 2-4
Layer 3 Addressing Information 2-4
Default VLAN 2-5
S
WITCHING
ECHNOLOGY
PLEX
® S
YSTEM
F
EATURES
P
ART
III A
How the LANplex® System Makes Flooding Decisions 2-5
VLAN Exception Flooding 2-6
Overlapped IP VLANs 2-7
Routing Between VLANs 2-8
VLAN Examples 2-10
BOUT
Modifying the Default VLAN 2-5
Example 1 2-10
Example 2 2-11
R
OUTING
P
ROTOCOLS
3
B
RIDGING
What Is Routing? 3-1
LANplex in a Subnetworked Environment 3-2
Integrating Bridging and Routing 3-3
Bridging and Routing Models 3-4
Traditional Bridging and Routing Model 3-4
LANplex Bridging and Routing Model 3-6
4
R
OUTING
IP Routing and the OSI Model 4-1
Elements of IP Routing 4-2
IP Addresses 4-2
Router Interfaces 4-4
Routing Table 4-5
Address Resolution Protocol (ARP) 4-7
IP Routing Transmission Errors 4-9
Routing with Classical IP over ATM 4-10
About Logical IP Subnets (LISs) 4-10
ATM ARP Servers 4-10
IP Routing References 4-11
AND
R
OUTING
WITH
IP T
Address Classes 4-3
Subnet Part of an IP Address 4-3
Static Routes 4-6
Dynamic Routes Using RIP 4-6
Default Route 4-7
Forwarding to Nodes within an LIS 4-11
IN
THE
ECHNOLOGY
LAN
PLEX
® S
YSTEM
5
R
OUTING
About IP Multicast Routing 5-1
IGMP 5-1
DVMRP 5-2
The MBONE 5-2
Multicast Routing
Algorithms 5-3
Flooding 5-3
Spanning Trees 5-3
Reverse Path Forwarding 5-4
Pruning 5-5
Multicast Interfaces 5-5
DVMRP Metric Value 5-5
Time-To-Live (TTL) Threshold 5-5
Rate Limit 5-6
Multicast Tunnels 5-6
WITH
IP M
ULTICAST
6
R
OUTING
IPX Routing in the NetWare® Environment 6-1
Internet Packet Exchange (IPX) 6-2
Routing Information Protocol (RIP) 6-3
Service Advertising Protocol (SAP) 6-3
How IPX Routing Works 6-4
IPX Packet Format 6-4
IPX Packet Delivery 6-6
The Elements of
IPX Routing 6-8
Router Interfaces 6-8
Routing Tables 6-8
Service Advertising Protocol 6-10
WITH
IPX
Sending Node’s Responsibility 6-6
Router’s Responsibility 6-7
Generating Routing Table Information 6-9
Selecting the Best Route 6-10
Internetwork Service Information 6-10
SAP Packet Structure 6-11
Server Information Table 6-13
Server Information Maintenance 6-14
7
R
OUTING
About AppleTalk® 7-1
AppleTalk® Network Elements 7-1
AppleTalk® Networks 7-2
AppleTalk® Nodes 7-2
AppleTalk® Zones 7-3
Seed Routers 7-4
AppleTalk Protocols 7-4
Physical Connectivity 7-5
The Datagram Delivery Protocol (DDP) 7-6
End-to-End Services 7-6
Presentation Layer 7-10
About AARP 7-10
IN
AN
Named Entities 7-2
Transport Layer Protocols 7-6
The Session Layer Protocols 7-9
A
PPLE
T
ALK
® E
NVIRONMENT
S
P
ART
IV A
8
A
Displaying VLAN Information 8-1
Defining VLAN Information 8-3
Modifying VLAN Information 8-4
Removing VLAN Information 8-5
9
A
Administering interfaces 9-1
Administering Routes 9-9
DMINISTERING
DMINISTERING
DMINISTERING
LIS Interfaces 9-2
Interface Characteristics 9-2
Displaying Interfaces 9-3
Defining an IP LIS Interface 9-4
Defining an IP VLAN Interface 9-6
Modifying an Interface 9-7
Removing an Interface 9-7
Adding an Advertisement Address 9-8
Removing an Advertisement Address 9-8
Adding a Permanent Virtual Circuit (PVC) 9-9
Removing a Permanent Virtual Circuit (PVC) 9-9
Displaying the Routing Table 9-11
E
VLAN
IP R
OUTING
XTENDED
S
WITCHING
F
EATURES
Defining a Static Route 9-11
Removing a Route 9-12
Flushing a Route 9-12
Setting the Default Route 9-12
Removing the Default Route 9-13
Administering the ARP Cache 9-13
Displaying the ARP Cache 9-14
Removing an ARP Cache Entry 9-14
Flushing the ARP Cache 9-15
Administering ATM ARP Servers 9-15
Displaying ATM ARP Servers 9-15
Defining an ATM ARP Server 9-16
Removing an ATM ARP Server 9-16
Displaying the ATM ARP Cache 9-17
Removing an ATM ARP Cache Entry 9-17
Flushing the ATM ARP Cache 9-18
Administering UDP Helper 9-18
Displaying UDP Helper Information 9-19
Defining a Port and an IP Forwarding Address 9-19
Removing a Port or an IP Forwarding Address 9-19
Setting the BOOTP Hop Count Limit 9-20
Setting the BOOTP Relay Threshold 9-20
Enabling and Disabling IP Routing 9-20
Enabling and Disabling ICMP Router Discovery 9-21
Setting the RIP Mode 9-21
Pinging an IP Station 9-22
Displaying IP Statistics 9-23
10
A
DMINISTERING
Enabling and Disabling DVMRP 10-2
Enabling and Disabling IGMP 10-2
Administering IP Multicast Interfaces 10-3
DVMRP Metric Value 10-3
Time To Live (TTL) Threshold 10-3
Rate Limit 10-4
Displaying Multicast Interfaces 10-4
Disabling Multicast Interfaces 10-5
Enabling Multicast Interfaces 10-5
Administering Multicast Tunnels 10-6
Displaying Multicast Tunnels 10-6
Defining a Multicast Tunnel 10-7
Removing a Multicast Tunnel 10-7
IP M
ULTICAST
R
OUTING
Displaying Routes 10-8
Displaying the Multicast Cache 10-9
11
A
DMINISTERING
Administering Interfaces 11-2
Displaying IPX Interfaces 11-3
Defining an IPX Interface 11-3
Modifying an Interface 11-4
Removing an Interface 11-4
Administering Routes 11-5
Displaying the Routing Table 11-6
Defining a Static Route 11-6
Removing a Route 11-7
Flushing Routes 11-7
Administering Servers 11-8
Displaying the Server Table 11-9
Defining a Static Server 11-9
Removing a Server 11-10
Flushing Servers 11-10
Setting IPX Forwarding 11-11
Setting the RIP Mode 11-11
Setting the Enhanced RIP Mode 11-12
Setting the SAP Mode 11-13
Displaying Statistics 11-14
Displaying IPX Summary Statistics 11-14
Displaying IPX RIP Statistics 11-15
Displaying IPX SAP Statistics 11-16
Displaying IPX Forwarding Statistics 11-17
IPX R
OUTING
12
A
DMINISTERING
Administering Interfaces 12-2
Displaying AppleTalk Interfaces 12-3
Defining an Interface 12-3
Removing an Interface 12-4
Administering Routes 12-5
Displaying the Routing Table 12-5
Flushing all Routes 12-6
Administering the AARP Cache 12-7
Displaying the AARP Cache 12-8
Removing an Entry in the Cache 12-9
Flushing All Cache Entries 12-9
Displaying the Zone Table 12-10
A
PPLE
T
ALK
® R
OUTING
P
ART
VR
Configuring Forwarding 12-11
Configuring Checksum 12-12
Pinging an AppleTalk Node 12-12
Viewing Appletalk Statistics 12-13
Displaying DDP Statistics 12-13
Displaying RTMP Information 12-14
Displaying ZIP Information 12-15
Displaying NBP Information 12-17
EMOTE
M
ONITORING
(RMON)
AND
THE
P
ART
LAN
13
R
What Is RMON? 13-1
Benefits of RMON 13-2
LANplex RMON Implementation 13-2
Management Information Base (MIB) 13-4
Alarms 13-6
VI A
A
T
On-line Technical Services A-1
Support from Your Network Supplier A-3
PLEX
EMOTE
3Com Transcend RMON Agents 13-3
MIB Objects 13-4
Setting Alarm Thresholds 13-7
Example of an Alarm Threshold 13-7
RMON Hysteresis Mechanism 13-8
® S
M
ONITORING
YSTEM
(RMON) T
PPENDIX
ECHNICAL
3Com Bulletin Board Service A-1
Access by Analog Modem A-1
Access by Digital Modem A-2
World Wide Web Site A-2
3ComForum on CompuServe® A-2
3ComFacts™ Automated Fax Service A-3
SUPPORT
ECHNOLOGY
Support from 3Com A-4
Returning Products for Repair A-4
INDEX
ABOUT THIS GUIDE
Introduction The LANplex® 2500 Ex tended Switching User Guide provides information
about the features included with the LANplex Extended Switching
software. These features include IP, IP Multicast, classical IP over ATM, IPX,
and AppleTalk routing, virtual LAN ( VLAN) configuration, and remote
monitoring (RMON).
Use this guide with the LANplex® 2500 Administration Console User Guide
when you configure your LANplex 2500 system.
See the LANplex® 2500 Software Installation and Release Notes for
information about how to install Extended Switching software on your
LANplex system.
Audience description This guide is intended for the system or network administrator who is
responsible for configuring, using, and managing the LANplex 2500 system. It
assumes a working knowledge of local area network (LAN) operations and a
familiarity with communications protocols used on interconnected LANs.
How to Use This
Guide
If the information in the release notes shipped with your product differs from
the information in this guide, follow the release notes.
The following table shows where to find specific information.
If you are looking for... Turn to...
An overview of Extended Switching features Chapter 1
Virtual LANs (VLANs) on the LANplex System Chapter 2
General routing and routing models in the LANplex system Chapter 3
IP routing strategies Chapter 4
IP multicast routing and its protocols Chapter 5
continued
2 ABOUT THIS GUIDE
If you are looking for... Turn to...
IPX routing and its protocols Chapter 6
AppleTalk routing, network elements, and protocols Chapter 7
How to administer VLANs Chapter 8
How to administer IP routing Chapter 9
How to administer IP mulitcast routing Chapter 10
How to administer IPX routing Chapter 11
How to administer AppleTalk routing Chapter 12
Remote Monitoring (RMON) Chapter 13
3Com Technical Support Appendix A
Conventions Table 1 and Table 2 list conventions that are used throughout this guide.
Table 1 Notice Icons
Icon Type Description
Information Note Information notes call attention to important features or
instructions.
Caution Cautions alert you to personal safety risk, system damage,
or loss of data.
Warning Warnings alert you to the risk of severe personal injury.
LANplex 2500 Documentation 3
Table 2 Text Conventions
Convention Description
“Enter” “Enter” means type something, then press the [Return] or [Enter] key.
“Syntax” vs. “Command” “Syntax” indicates that the general command syntax form is provided. You must
evaluate the syntax and supply the appropriate value; for example:
Set the date by using the following syntax:
mm/DD/yy hh:mm:ss xm
“Command” indicates that all variables in the command syntax form have been
supplied and you can enter the command as shown in text; for example:
To update the system software, enter the following command:
system software Update
screen display This typeface indicates text that appears on your terminal screen; for example:
NetLogin:
commands This typeface indicates commands that you enter; for example:
bridge port stpState
Italic Italic is used to denote emphasis and buttons.
Keys When specific keys are referred to in the text, they are called out by their labels, such
as “the Return key” or “the Escape key,” or they may be shown as [Return] or [Esc].
If two or more keys are to be pressed simultaneously, the keys are linked with a plus
sign (+), for example:
Press [Ctrl]+[Alt]+[Del].
LANplex 2500
Documentation
The following documents comprise the LANplex 2500 documentation set.
If you want to order a document that you do not have or order additional
documents, contact your sales representative for assistance.
■ LANplex® 2500 Unpacking Instructions
Describe how to unpack your LANplex system. It also provides you with
an inventory list of all the items shipped with your system. (Shipped
with system/Part No. 801-00353-00)
4 ABOUT THIS GUIDE
■ LANplex® 2500 Software Release Notes
Provide information about the software release, including new features and
bug fixes. It also provides information about any changes to the LANplex
system’s documentation. (Shipped with system)
■ LANplex® 2500 Getting Started
Describes all the procedures necessary for installing, cabling, powering up,
configuring management access to, and troubleshooting your LANplex system. (Shipped with system/Part No. 801-00355-000)
■ LANplex® 2500 Operation Guide
Provides information to help you understand system management and
administration, bridging, Fast Ethernet, ATM, and FDDI technology. I t also
describes how these concepts are implemented in the LANplex system.
(Shipped with system/Part No. 801-00344-000)
■ LANplex® 2500 Administration Console User Guide
Provides information about using the Administration Console to configure
and manage your LANplex system. (Shipped with system/Part No.
801-00322-000)
■ LANplex® 2500 Extended Switching User Guide ( This book)
Describes® how the routing protocols, VLAN, and RMON are implemented
in the LANplex system and provides information about using the
Administration Console to configure and manage these features. (shipped
with the option package/Part No. 801-00343-000)
■ LANplex® 2500 Intelligent Switching Administration Console Command Quick
Reference card
Contains the Administration Console Intelligent Switching commands for
the LANplex system. (Shipped with the system/Part No. 801-000318-000)
■ LANplex® 2500 Extended Switching ADMINISTRATION CONSOLE Command Quick
Reference card
Contains the Administration Console Extended Switching commands for the
LANplex system. (Shipped with the option package/Part No. 801-00319-000)
Documentation Comments 5
■ Module Installation Guides
Provide an overview, installation instructions, LED status information, and
pin-out information for the particular option module. (Shipped with individual modules)
Documentation
Comments
Example: LANplex® 2500 Operation Guide
Your suggestions are very important to us and will help mak e our
documentation more useful to you. Please email comments about this
document to 3Com at: sdtechpubs_comments@3Mail.3Com.com
Please include the following information when commenting:
■ Document title
■ Document part number (listed on back cover of document)
■ Page number (if appropriate)
Part No. 801-00344-000
Page 2-5 (chapter 2, page 5)
6 ABOUT THIS GUIDE
1
LANPLEX® EXTENDED SWITCHING
F
EATURES
This chapter provides an overview of the Extended Switching software, and
describes the enhanced Administration Console menus.
About LANplex
Extended
Switching
The LANplex Extended Switching software replaces your existing LANplex
software and adds new functionality to your system. Extended Switching
software contains all the features of LANplex Intelligent Switching software,
in addition to:
■ Virtual LANs ( VLANs)
■ Internet Protocol (IP) Routing (an enhanced version of IP from the standard
system software)
■ IP multicast routing
■ Classical IP routing over Asynchronous Transfer Mode (ATM)
■ Internet Packet Exchange (IPX) routing
■ AppleTalk® routing
■ Remote Monitoring (RMON)
For information on how to gain access to online help, to use scripts, and to
exit from the Administration Console, see the LANplex® 2500 Administration
Console User Guide.
See the LANplex® 2500 Software Installation and Release Notes for
information about how to install Extended Switching software on your
LANplex system.
1-2 CHAPTER 1: LANPLEX® EXTENDED SWITCHING FEATURES
Using Menus When you gain access to the Administration Console, the top-level menu
appears. The Extended Switching software contains top-level menus and
additions to the Bridge and IP menu options not available with Intelligent
Switching software:
Option Descriptions
Menu options:
-------------------------------------------------------------------system - Administer system-level functions
ethernet- Administer Ethernet ports
Menu options vary
by level of access
fddi - Administer FDDI resources
ATM - Administer ATM resources
bridge - Administer bridging/VLANs
ip - Administer IP
ipx - Administer IPX
appletalk- Administer Appletalk
snmp - Administer SNMP
analyzer- Administer Roving Analysis
script - Run a script of console commands
logout - Logout of the Administration Console
Type ? for help.
--------------------------------------------------------------------
Select a menu option:
The following sections show the enhanced menus provided with Extended
Switching software. All other menu items appear in the LANplex® 2500
Administration Console User Guide.
The RMON feature is available through SNMP only. This feature is not
available through the Administration Console. See Chapter 13, Remote
Monitoring (RMON) Technology, for more information about this feature.
Using Menus 1-3
Bridge Menu From the bridge menu, you can view information about and configure
Ethernet LANs, including VLANs. Figure 1-1 shows the bridge menu.
Top-Level Menu bridge menu interface menu
system display summary
ethernet mode detail
fddi ipFragmentation define
atm ipxSnapTranslation modify
➧ bridge
ip agingTime
ipx stpState
appletalk stpPriority
snmp stpMaxAge
analyzer stpHelloTime
script stpForwardDelay
logout stpGroupAddress
Figure 1-1 Bridge Menu Hierarchy
addressThreshold remove
port
packetFilter
vlan
1-4 CHAPTER 1: LANPLEX® EXTENDED SWITCHING FEATURES
IP Menu From the ip menu, you can view information about and configure Internet
Protocol (IP) interfaces and routes as well as IP Multicast routing. You can
administer the Address Resolution Protocol (ARP), the Routing Information
Protocol (RIP), UDP Helper, IP Forwarding, and ping IP stations. You can also
define ATM ARP servers from the ip menu if you are running classical IP
over ATM. Figure 1-2 shows the ip menu. To define a new IP inter face, for
example, enter ip at the top-level menu, inter face at the ip menu, and then
define at the interface menu.
Top-Level Menu ip menu interface menu
system
ethernet
fddi
atm
bridge
➧ ip ➧udpHelper
ipx routing removeAdvertisement
appletalk icmpRouterDiscovery addPvc
snmp rip removePvc
analyzer ping
script statistics route menu
logout display
Figure 1-2 IP Menu Hierarchy
➧ interface
➧ route
➧ arp
➧ atmArpServer
➧ multicast
summary
detail
define
modify
remove
addAdvertisement
static
remove
flush
default
noDefault
arp menu
display
remove
flush
atmArpServer
display
define
remove
arp
multicast
dvmrp
igmp
interfaces
tunnel
RouteDisplay
cacheDisplay
udpHelper menu
display
define
remove
hopCountLimit
threshold
Using Menus 1-5
IPX Menu From the ipx menu, you can view information about and configure Internet
Packet Exchange (IPX) interfaces, routes, and servers. You can also
administer the Routing Information Protocol (RIP), Enhanced RIP mode,
Service Advertising Protocol (SAP), and statistics. Figure 1-3 shows the IPX
menu. For example, to define a new IPX inter face, enter ipx at the top-level
menu, interface at the ipx menu, and then define at the interface menu.
Top-Level Menu ipx menu interface menu
system
ethernet
fddi
atm forwarding remove
bridge rip
ip enhanced
➧ ipx
appletalk
snmp static
analyzer remove
script flush
logout
➧ interface
➧ route
➧ server
sap route menu
➧ statistics
Figure 1-3 IPX Menu Hierarchy
display
define
modify
display
server menu
display
static
remove
flush
statistics menu
summary
rip
sap
forwarding
1-6 CHAPTER 1: LANPLEX® EXTENDED SWITCHING FEATURES
Appletalk Menu From the appletalk menu, you can view information about and configure
Appletalk interfaces, routes, and zones. You can also administer the
Appletalk Address Resolution Protocol (AARP), AppleTalk forwarding, and
statistics. Figure 1-4 shows the Appletalk menu. For example, to define a
new AppleTalk interface, you would enter appletalk at the top-level menu,
interface at the AppleTalk menu, then define at the inter face menu.
Top-Level Menu appletalk menu interface menu
system
ethernet
fddi
atm zone
bridge forwarding
ip checksum route menu
ipx ping display
➧ interface
➧ route
➧ aarp
➧ appletalk ➧statistics
snmp
analyzer aarp menu
script display
logout remove
display
define
remove
flush
flush
statistics menu
ddp
rtmp
zip
nbp
Figure 1-4 Appletalk Menu Hierarchy
VLANS ON THE
2
About VLANs The VLAN concept in LAN technology helps minimize broadcast and
LAN
This chapter contains:
■ A description of Virtual LAN ( VLAN) concepts and their operational aspects
in the LANplex® 2500 system
■ Examples of VLAN configurations
multicast traffic. It also makes end-station moves, adds, and changes easier
for the network administrator.
In the LANplex system, VLANs allow you to:
■ Create independent broadcast domains to optimize network performance
and create firewalls
■ Form flexible user groups independent of the users’ physical network
location
PLEX
®
SYSTEM
Types of VLANs You can use several types of VLANs to group users. These types include:
■ Port group VLANs
■ MAC address group VLANs
■ Application-oriented VLANs
■ Protocol-sensitive VLANs
Port Group VLANs
Port group VLANs group together one or more switch ports. This simple
implementation of VLANs requires little configuration. All frames received
on a port are grouped together. For example, all frames received on a port
that is part of a port group are kept within that por t group, regardless of
2-2 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM
the data contained in the frames. Port groups are useful when traffic
patterns are known to be directly associated with particular por ts. They can
benefit the user by restricting traffic based on a set of simple rules.
MAC Address Group VLANS
VLANs allow a switch to make filtering decisions based on grouping MAC
addresses together. These MAC address groups can be configured so that
stations in the group can only communicate with each other or with
specific network resources. This solution is good for security. It allows the
VLAN association to move with the station. However,
MAC-address-grouped VLANs may require complex configuration in
comparison to other types of VLANs.
Port group and MAC address group VLANs are supported using the packet
filtering capabilities in the LANplex system. For information on port group
and MAC address group filtering, refer to your LANplex Operation Guide and
LANplex Administration Console User Guide.
Application-Oriented VLANS
Using the LANplex filtering capability, application-specific traffic such as
telnet traffic or FTP traffic can be filtered based on higher-layer information.
You create this application-oriented VLAN by configuring packet filters that
specify data and offsets of the data within received packets. For example, to
use a filter on a particular port for all telnet traffic, create a a filter that
discards all TCP traffic received on the telnet port.
IP multicast routing and autocast VLANs are additional VLAN features in the
LANplex that can be used to group IP multicast traffic for specific
applications. For more information on how the LANplex system manages IP
Multicast traffic, see Chapter 8.
Protocol-Sensitive VLANS
When the LANplex system receives data that has a broadcast, multicast, or
unknown destination address, it forwards the data to all ports. This process
is referred to as bridge flooding.
Protocol-sensitive VLANs group one or more switch ports together for a
specified network layer 3 protocol, such as IP or AppleTalk. These VLANs
make flooding decisions based on the network layer protocol of the frame.
In addition, for IP VLANs, you can also make flooding decisions based on
About VLANs 2-3
layer 3 subnet address information. Protocol-sensitive VLANs allow the
restriction of flood traffic for both routable and nonroutable protocols. They
have a relatively simple configuration comprising one or more protocols
and groups of switch ports. These protocol-sensitive VLANs operate
independent of each other. Additionally, the same switch por t can belong
to multiple VLANs. For example, you can assign port 1 on a LANplex to
several IP subnet VLANs, plus one IPX VLAN, one AppleTalk VLAN, and one
NetBIOS VLAN. In a multiprotocol environment, protocol-sensitive VLANs
can be very effective for controlling broadcast and multicast flooding.
Two or more types of VLANs can coexist in the LANplex system. When
associating received data with a particular VLAN configuration in a multiple
VLAN configuration, port group, MAC address group, and
application-oriented VLANs always take precedence over protocol-sensitive
VLANs.
LANplex
Protocol-Sensitive
VLAN Configuration
The LANplex protocol-sensitive VLAN configuration includes three elements:
protocol suite, switch ports, layer 3 addressing information for IP VLANs.
Protocol Suite
The protocol suite describes which protocol entities can comprise a
protocol-sensitive VLAN. For example, LANplex VLANs support the IP
protocol suite, which is made up of the IP, ARP, and RARP protocols.
Table 2-1 lists the protocol suites that the LANplex suppor ts, as well as the
protocol types included in each protocol suite.
Table 2-1 Supported Protocols for VLAN Configuration
Protocol Suite Protocol Types
IP IP, ARP, RARP (Ethertype, SNAP PID)
Novell® IPX IPX (Ethertype, DSAP, SNAP PID)
AppleTalk® DDP, AARP (Ethertype, SNAP PID)
Xerox® XNS XNS IDP, XNS Address Translation, XNS Compatibility
(Ethertype, SNAP PID)
DECnet™ DEC MOP, DEC Phase IV, DEC LAT, DEC LAVC (Ethertype,
SNAP PID)
SNA SNA Services over Ethernet (Ethertype)
Banyan VINES® Banyan (Ethertype, DSAP, SNAP PID)
continued
2-4 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM
Table 2-1 Supported Protocols for VLAN Configuration (continued)
Protocol Suite Protocol Types
X25 X.25 Layer 3 (Ethertype)
NetBIOS™ NetBIOS (DSAP)
Default Default (all protocol types)
Switch Ports
A group of switch ports is any combination of switch ports on the LANplex
system. Included are switch ports created as ATM LAN Emulation Clients
(ATM LECs). VLANs do not support media implementations that do not run
over switch (bridge) ports, for example, ATM Logical IP Subnets (ATM LISs).
Layer 3 Addressing Information
For IP VLANs only, the LANplex system optionally suppor ts configuring of
individual IP VLANs with network layer subnet addresses. With this
additional layer 3 information, you can create independent IP VLANs that
share the same switch ports for multiple IP VLANs. Data is flooded according
to both the protocol (IP) and the layer 3 information in the IP header to
distinguish among multiple IP VLANs on the same switch port. This
configuration is discussed later in the section “Overlapped IP VLANs.”
About VLANs 2-5
Default VLAN When you star t up the LANplex system, the system automatically creates a
VLAN interface called the default VLAN. Initially, the default VLAN includes
all of the switch ports in the system. In the LANplex system, the default
VLAN serves to define:
■ The flood domain for protocols not supported by any VLAN in the system
■ The flood domain for protocols supported by a VLAN in the system but
received on nonmember ports
Both cases represent exception flooding conditions that are described in
the following sections.
Modifying the Default VLAN
New switch ports can dynamically appear in the LANplex system if you
insert a daughter LAN card or create an ATM LEC. When a new switch port
that is not part of a default VLAN appears in the system at initialization, the
system software adds that switch port to the first default VLAN defined in
the system.
How the LANplex®
System Makes
Flooding Decisions
LANplex VLANs also allow you to modify the initial default VLAN to form two
or more subsets of switch ports. If you remove the default VLAN and no other
VLANs are defined for the system, no flooding of traffic can occur.
Protocol-sensitive VLANs directly affect how the LANplex system performs
flooding. Without protocol-sensitive VLANs, the flooding process is to
forward data to all switch ports in the system. With protocol-sensitive
VLANs, the flooding process follows this model:
■ As a frame is received that needs to be flooded, it is decoded to determine
its protocol type.
■ If a VLAN exists for that protocol in the LANplex system and the frame’s
source port is a member of the VLAN, the frame is flooded according to the
group of ports assigned to that VLAN.
■ If a VLAN exists for that protocol in the LANplex system but the frame’s
source port is not a member of the VLAN definition, then the frame is
flooded according to the default VLAN assigned to that port.
■ If the protocol type of the received frame has no VLAN defined for it in the
system, the frame is flooded to the Default VLAN for the receive port.
2-6 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM
This example shows how flooding decisions are made according to VLANs
set up by protocol (assuming an 18-port switch):
Data received on... Is flooded on... Because...
IP - port 1 VLAN 2 IP data received matches IP VLAN on the
IPX - port 11 VLAN 3 IPX data received matches IPX VLAN on the
XNS - port 1 VLAN 1 XNS data received matches no protocol
Index VLAN Ports
1 Default 1 - 18
2 IP 1 - 12
3 IPX 11 - 16
source port.
source port.
VLAN, so the Default VLAN is used.
VLAN Exception
Flooding
If data arrives on a switch port for a certain protocol and VLANs for that
protocol are defined in the system but not on that switch port, the default
VLAN defines the flooding domain for that data. This case is called VLAN
exception flooding.
This example shows how the VLAN exception flooding decision is made
(assuming an 18-port switch):
Index VLAN Ports
1 Default 1 - 18
2 IP 1 - 10
About VLANs 2-7
Data received on... Is flooded on... Because...
XNS - port 1 VLAN 1 XNS data does not match any defined VLAN
in the system.
IP - port 2 VLAN 2 IP data received matches IP VLAN 2 for
source ports 1 - 10.
IP - port 12 VLAN 1 IP data received on source port 12 does not
match any defined source port for IP VLAN,
so the Default VLAN is used.
Overlapped IP
VLANs
The LANplex system also gives you the ability to assign network layer
information to IP VLANs. This capability allows network administrators to
manage their VLANs by subnet. Flooding decisions are made by first
matching the incoming frame using the protocol (IP) and then matching it
with layer 3 subnet information. I f received data is IP but does not match
any defined IP subnet VLAN, it is flooded within all IP VLANs using the
relevant switch port.
For example, two IP VLANs can be configured for ports 1-10 as follows:
IP VLAN 1 - Subnet 158.101.112.0, por ts 1-10
IP VLAN 2 - Subnet 158.101.113.0, por ts 1-10
This example shows how flooding decisions are made using overlapping IP
VLANs (assuming a 12-port switch):
Network
Index VLAN
1 Default none 1 - 12
2 IP 158.103.122.0/
3 IP 158.103.123.0/
Address/Mask
255.255.255.0
255.255.255.0
Ports
1 - 6
6 - 12
2-8 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM
Data received on... Is flooded on... Because...
IP subnet
158.103.122.2
on port 6
IP subnet
158.103.123.2
on port 6
IP subnet
158.103.124.2
on port 6
IPX on port 6 VLAN 1 IPX frame does not match any defined VLAN.
As shown in this example, when the subnet address of an IP packet does
not match any subnet address of any defined IP VLAN in the system, it is
flooded to all of the IP VLANs that share the source switch port, in this case,
port 6.
VLAN 2 IP network layer matches layer 3 address for
VLAN 2.
VLAN 3 IP network layer matches layer 3 address for
VLAN 3.
VLAN 2 and
VLAN 3
IP network layer does not match any layer 3
address for IP VLANs.
Routing Between
VLANs
The only way for stations that are in two different VLANs to communicate is
to route between them. The LANplex system supports internal routing
among IP, IPX, and AppleTalk VLANs. If VLANs are configured for other
routable network layer protocols, they can communicate between them
only via an external router.
The LANplex routing model lets you configure routing protocol interfaces
based on a VLAN defined for that protocol. To assign a routing interface, you
must first create a VLAN for that protocol and then associate it with that
interface.
For example, to create an IP inter face that can route through a VLAN:
1 Create an IP VLAN for a group of switch ports.
This IP VLAN does not need to contain layer 3 information unless you want
to further restrict flooding according to the layer 3 subnet address.
2 Configure an IP interface with a network address, subnet mask, broadcast
address, cost, and type (VLAN). Select an IP VLAN to “bind” to that IP
interface.
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