D-Link DGS-3308 User Manual

DGS-3308 Series

8-Port Gigabit Layer 3 Switch

User’s Guide

First Edition (December 2001)

651FG3308015

Printed In Taiwan

RECYCLABLE

Wichtige Sicherheitshinweise

1. Bitte lesen Sie sich diese Hinweise sorgfältig durch.

2. Heben Sie diese Anleitung für den spätern Gebrauch auf.

3. Vor jedem Reinigen ist das Gerät vom Stromnetz zu trennen. Vervenden Sie keine Flüssig- oder Aerosolreiniger. Am besten dient ein angefeuchtetes Tuch zur Reinigung.

4. Um eine Beschädigung des Gerätes zu vermeiden sollten Sie nur Zubehörteile verwenden, die vom Hersteller zugelassen sind.

5. Das Gerät is vor Feuchtigkeit zu schützen.

6. Bei der Aufstellung des Gerätes ist auf sichern Stand zu achten. Ein Kippen oder Fallen könnte Verletzungen hervorrufen. Verwenden Sie nur sichere Standorte und beachten Sie die Aufstellhinweise des Herstellers.

7. Die Belüftungsöffnungen dienen zur Luftzirkulation die das Gerät vor Überhitzung schützt. Sorgen Sie dafür, daß diese Öffnungen nicht abgedeckt werden.

8. Beachten Sie beim Anschluß an das Stromnetz die Anschlußwerte.

9. Die Netzanschlußsteckdose muß aus Gründen der elektrischen Sicherheit einen Schutzleiterkontakt haben.

10. Verlegen Sie die Netzanschlußleitung so, daß niemand darüber fallen kann. Es sollete auch nichts auf der Leitung abgestellt werden.

11. Alle Hinweise und Warnungen die sich am Geräten befinden sind zu beachten.

12. Wird das Gerät über einen längeren Zeitraum nicht benutzt, sollten Sie es vom Stromnetz trennen. Somit wird im Falle einer Überspannung eine Beschädigung vermieden.

13. Durch die Lüftungsöffnungen dürfen niemals Gegenstände oder Flüssigkeiten in das Gerät gelangen. Dies könnte einen Brand bzw. Elektrischen Schlag auslösen.

14. Öffnen Sie niemals das Gerät. Das Gerät darf aus Gründen der elektrischen Sicherheit nur von authorisiertem Servicepersonal geöffnet werden.

15. Wenn folgende Situationen auftreten ist das Gerät vom Stromnetz zu trennen und von einer qualifizierten Servicestelle zu überprüfen: a – Netzkabel oder Netzstecker sint beschädigt. b – Flüssigkeit ist in das Gerät eingedrungen. c – Das Gerät war Feuchtigkeit ausgesetzt. d – Wenn das Gerät nicht der Bedienungsanleitung ensprechend funktioniert oder Sie mit Hilfe dieser Anleitung keine Verbesserung erzielen. e – Das Gerät ist gefallen und/oder das Gehäuse ist beschädigt. f – Wenn das Gerät deutliche Anzeichen eines Defektes aufweist.

16. Bei Reparaturen dürfen nur Orginalersatzteile bzw. den Orginalteilen entsprechende Teile verwendet werden. Der Einsatz von ungeeigneten Ersatzteilen kann eine weitere Beschädigung hervorrufen.

17. Wenden Sie sich mit allen Fragen die Service und Repartur betreffen an Ihren Servicepartner. Somit stellen Sie die Betriebssicherheit des Gerätes sicher.

18. Zum Netzanschluß dieses Gerätes ist eine geprüfte Leitung zu verwenden, Für einen Nennstrom bis 6A und einem Gerätegewicht grßer 3kg ist eine Leitung nicht leichter als H05VV-F, 3G, 0.75mm2 einzusetzen.

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IF THE D-LINK PRODUCT DOES NOT OPERATE AS WARRANTED ABOVE, THE CUSTOMER'S SOLE REMEDY SHALL BE, AT D-LINK'S OPTION, REPAIR OR REPLACEMENT. THE FOREGOING WARRANTIES AND REMEDIES ARE EXCLUSIVE AND ARE IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, EITHER IN FACT OR BY OPERATION OF LAW, STATUTORY OR OTHERWISE, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. D-LINK NEITHER ASSUMES NOR AUTHORIZES ANY OTHER PERSON TO ASSUME FOR IT ANY OTHER LIABILITY IN CONNECTION WITH THE SALE, INSTALLATION MAINTENANCE OR USE OF D-LINK'S PRODUCTS D-LINK SHALL NOT BE LIABLE UNDER THIS WARRANTY IF ITS TESTING AND EXAMINATION DISCLOSE THAT THE ALLEGED DEFECT IN THE PRODUCT DOES NOT EXIST OR WAS CAUSED BY THE CUSTOMER'S OR ANY THIRD PERSON'S MISUSE, NEGLECT, IMPROPER INSTALLATION OR TESTING, UNAUTHORIZED ATTEMPTS TO REPAIR, OR ANY OTHER CAUSE BEYOND THE RANGE OF THE INTENDE D USE, OR BY ACCIDENT, FIRE, LIGHTNING OR OTHER HAZARD.

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IN NO EVENT WILL D-LINK BE LIABLE FOR ANY DAMAGES, INCLUDING LOSS OF DATA, LOSS OF PROFITS, COST OF COVER OR OTHER INCIDENTAL, CONSEQUENTIAL OR INDIRECT DAMAGES ARISING OUT THE INSTALLATION, MAINTENANCE, USE, PERFORMANCE, FAILURE OR INTERRUPTION OF A D- LINK PRODUCT, HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY. THIS LIMITATION WILL APPLY EVEN IF DLINK HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. IF YOU PURCHASED A D-LINK PRODUCT IN THE UNITED STATES, SOME STATES DO NOT ALLOW THE LIMITATION OR EXCLUSION OF LIABILITY FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THE ABOVE LIMITATION MAY NOT APPLY TO YOU.

Limited Warranty

Hardware:

D-Link warrants each of its hardware products to be free from defects in workmanship and materials under normal use and service for a period commencing on the date of purchase from D-Link or its Authorized Reseller and extending for the length of time stipulated by the Authorized Reseller or D-Link Branch Office nearest to the place of purchase.

This Warranty applies on the condition that the product Registration Card is filled out and returned to a D-Link office within ninety (90) days of purchase. A list of D-Link offices is provided at the back of this manual, together with a copy of the Registration Card.

If the product proves defective within the applicable warranty period, D-Link will provide repair or replacement of the product. D-Link shall have the sole discretion whether to repair or replace, and replacement product may be new or reconditioned. Replacement product shall be of equivalent or better specifications, relative to the defective product, but need not be identical. Any product or part repaired by D-Link pursuant to this warrant y shall have a warranty period of not less than 90 days, from date of such repair, irrespective of any earlier expiration of original warranty period. When D-Link provides replacement, then the defective product becomes the property of D-Link.

Warranty se rvice may be obtained by contacting a D-Link office within the applicable warranty period, and requesting a Return Material Authorization (RMA) number. If a Registration Card for the product in question has not been returned to D-Link, then a proof of pur chase (such as a copy of the dated purchase invoice) must be provided. If Purchaser's circumstances require special handling of warranty correction, then at the time of requesting RMA number, Purchaser may also propose special procedure as may be suitable to the case.

After an RMA number is issued, the defective product must be packaged securely in the original or other suitable shipping package to ensure that it will not be damaged in transit, and the RMA number must be prominently marked on the outside of the package. The package must be mailed or otherwise shipped to D-Link with all costs of mailing/shipping/insurance prepaid. D-Link shall never be responsible for any software, firmware, information, or memory data of Purchaser contained in, stored on, or integrated with any product returned to D-Link pursuant to this warranty.

Any package returned to D-Link without an RMA number will be rejected and shipped back to Purchaser at Purchaser's expense, and D-Link reserves the right in such a case to levy a reasonable handling charge in addition mailing or shipping costs.

Software:

Warranty service for software products may be obtained by contacting a D-Link office within the applicable warranty period. A list of D-Link offices is provided at the back of thi s manual, together with a copy of the Registration Card. If a Registration Card for the product in question has not been returned to a D-Link office, then a proof of purchase (such as a copy of the dated purchase invoice) must be provided when requesting warranty service. The term "purchase" in this software warranty refers to the purchase transaction and resulting license to use such software.

D-Link warrants that its software products will perform in substantial conformance with the applicable product documentation provided by D-Link with such software product, for a period of ninety (90) days from the date of purchase from D-Link or its Authorized Reseller. D-Link warrants the magnetic media, on which D-Link provides its software product, against failure during the same warranty period. This warranty applies to purchased software, and to replacement software provided by D-Link pursuant to this warranty, but shall not apply to any update or replacement which may be provided for download via the Internet, or to any update which may otherwise be provided free of charge.

D-Link's sole obligation under this software warranty shall be to replace any defective software product with product which substantially conforms to D-Link's applicable product documentation. Purchaser assumes responsibility for the selection of appropriate application and system/platform software and associated reference materials. D-Link makes no warranty that its software products will work in combination with any hardware, or any application or system/platform software product provided by any third party, excepting only such products as are expressly represented, in D-Link's applicable product

documentation as being compatible. D-Link's obligation under this warranty shall be a reasonable effort to provide compatibility, but D-Link shall have no obligation to provide compatibility when there is fault in the third-party hardware or software. D-Link makes no warranty that operation of its software products will be uninterrupted or absolutely error-free, and no warranty that all defects in the software product, within or without the scope of D-Link's applicable product documentation, will be corrected.

D-Link Offices for Registration and Warranty Service

The product's Registration Card, provided at the back of this manual, must be sent to a D-Link office. To obtain an RMA number for warranty service as to a hardware product, or to obtain warranty service as to a software product, contact the D-Link office nearest you. An address/telephone/fax/e -mail/Web site list of D-Link offices is provided in the back of this manual.

Trademarks

Copyright 2001 D-Link Corporation. Contents subject to change without prior notice. D-Link is a registered trademark of D-Link Corporation/D-Link Systems, Inc. All other trademarks belong to their respective proprietors.

No part of this publication may be reproduced in any form or by any means or used to make any derivative such as translation, transformation, or adaptation without permission from D-Link Corporation/D-Link Systems Inc., as stipulated by the United States Copyright Act of 1976.

FCC Warning

This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with this user’s guide, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense.

CE Mark Warning

This is a Class A product. In a domestic environment, this product may cause radio interference in which case the user may be required to take adequate measures.

VCCI Warning

BSMI Warning

Table of Contents

About This Guide...............................................................................................................................................................................................1

Overview of this User’s Guide.....................................................................................................................................................................1

Introduction.........................................................................................................................................................................................................2

Layer 3 Switching...........................................................................................................................................................................................2

The Functions of a Layer 3 Switch..........................................................................................................................................................3

Features...........................................................................................................................................................................................................3

Ports...............................................................................................................................................................................................................3

Performance Features...................................................................................................................................................................................4

Layer 2 Switching Features......................................................................................................................................................................4

Layer 3 Switching Features......................................................................................................................................................................4

Traffic Classification and Prioritization...............................................................................................................................................5

Management................................................................................................................................................................................................5

Optional Redundant Power Supply........................................................................................................................................................6

Fast Ethernet Technology.............................................................................................................................................................................6

Gigabit Ethernet Technology.......................................................................................................................................................................6

Unpacking and Setup........................................................................................................................................................................................7

Unpacking........................................................................................................................................................................................................7

Installation......................................................................................................................................................................................................7

Desktop or Shelf Installation...................................................................................................................................................................7

Rack Installation........................................................................................................................................................................................8

Power on...........................................................................................................................................................................................................9

Power Failure...............................................................................................................................................................................................9

Identifying External Components................................................................................................................................................................10

Front Panel....................................................................................................................................................................................................10

Rear Panel.....................................................................................................................................................................................................10

Side Panels....................................................................................................................................................................................................11

LED Indicators..............................................................................................................................................................................................11

Connecting The Switch...................................................................................................................................................................................12

PC to Switch..................................................................................................................................................................................................12

Switch to Switch (other devices)...............................................................................................................................................................12

Switch Management and Operating Concepts..........................................................................................................................................14

Local Console Management ...................................................................................................................................................................14

IP Addresses and SNMP Community Names...................................................................................................................................15

Traps............................................................................................................................................................................................................16

MIBs............................................................................................................................................................................................................17

SNMP..........................................................................................................................................................................................................17

Packet Forwarding....................................................................................................................................................................................18

MAC Address Aging Time......................................................................................................................................................................18

Filtering......................................................................................................................................................................................................18

IP Addressing and Subnetting...............................................................................................................................................................19

802.1Q VLANs .........................................................................................................................................................................................23

Spanning Tree Protocol............................................................................................................................................................................28

Internet Protocols......................................................................................................................................................................................34

The Domain Name System.....................................................................................................................................................................42

DHCP Servers............................................................................................................................................................................................42

Routing........................................................................................................................................................................................................42

ARP..............................................................................................................................................................................................................43

Multicasting...............................................................................................................................................................................................43

Internet Group Management Protocol (IGMP)...................................................................................................................................45

Multicast Routing Algorithms...............................................................................................................................................................46

Multicast Routing Protocols...................................................................................................................................................................48

Routing Protocols......................................................................................................................................................................................48

Configuring the Switch Using the Console Interface...............................................................................................................................54

Before You Start...........................................................................................................................................................................................54

General Deployment Strategy................................................................................................................................................................54

VLAN Layout ............................................................................................................................................................................................55

Assigning IP Network Addresses and Subnet Masks to VLANs..................................................................................................55

Defining Static Routes.............................................................................................................................................................................55

Connecting to the Switch............................................................................................................................................................................56

Console Usage Conventions ...................................................................................................................................................................56

Setup User Accounts...................................................................................................................................................................................58

User Accounts Management ..................................................................................................................................................................59

Save Changes................................................................................................................................................................................................60

Reboot.............................................................................................................................................................................................................62

Logging Onto The Switch Console............................................................................................................................................................63

Updating or Deleting User Accounts....................................................................................................................................................63

Viewing Current User Accounts............................................................................................................................................................64

Deleting a User Account..........................................................................................................................................................................65

Setting Up The Switch................................................................................................................................................................................65

Basic Setup................................................................................................................................................................................................65

Switch Information...................................................................................................................................................................................66

IP Setup.......................................................................................................................................................................................................67

Remote Management Setup...................................................................................................................................................................69

Configure Ports..........................................................................................................................................................................................70

Serial Port Settings..................................................................................................................................................................................71

Switch Operation Mode..............................................................................................................................................................................72

Changing the Switch Operation Mode.................................................................................................................................................73

Layer 2 Switch Settings ..........................................................................................................................................................................76

Layer 3 Switch Mode - Setup RIP .........................................................................................................................................................77

Advanced Setup............................................................................................................................................................................................79

Configuring VLANs..................................................................................................................................................................................79

VLANs by Switch Operating Mode – Layer 2 Only and IP Routing..............................................................................................79

Setting Up IP Interfaces.............................................................................................................................................................................86

Layer 2 Multicast Setup.........................................................................................................................................................................89

IGMP Snooping Settings – by VLAN...................................................................................................................................................89

IEEE 802.1Q Multicast Forwarding.....................................................................................................................................................91

Static Router Port.....................................................................................................................................................................................92

Layer 3 Multicasting................................................................................................................................................................................93

Mirroring.....................................................................................................................................................................................................101

Priority .........................................................................................................................................................................................................103

Layer 2 Filtering....................................................................................................................................................................................104

Layer 3 (IP Routing) Filtering.............................................................................................................................................................105

Forwarding..................................................................................................................................................................................................108

Layer 2 Forwarding...............................................................................................................................................................................108

IP Routing Forwarding..........................................................................................................................................................................109

MAC Address Forwarding...................................................................................................................................................................109

Spanning Tree............................................................................................................................................................................................112

Switch Spanning Tree Settings ..........................................................................................................................................................112

Port Group Spanning Tree Settings...................................................................................................................................................114

Port Trunking.............................................................................................................................................................................................115

Switch Utilities.........................................................................................................................................................................................117

Layer 2 Switch Utilities.......................................................................................................................................................................117

Upgrade Firmware from TFTP Server..............................................................................................................................................117

Download Configuration File from TFTP Server............................................................................................................................118

Upload Configuration File to TFTP Server......................................................................................................................................119

Save Log to TFTP Server......................................................................................................................................................................120

Ping...........................................................................................................................................................................................................121

Layer 3 Utilities.....................................................................................................................................................................................122

BOOTP/DHCP Relay .............................................................................................................................................................................122

DNS Relay...............................................................................................................................................................................................124

Network Monitoring.................................................................................................................................................................................126

Layer 2 Network Monitoring...............................................................................................................................................................126

Port Utilization......................................................................................................................................................................................127

Port Error Packets.................................................................................................................................................................................128

Port Packet Analysis Table................................................................................................................................................................. 128

MAC Address Forwarding Table.......................................................................................................................................................129

IGMP Snooping.......................................................................................................................................................................................130

Switch History........................................................................................................................................................................................131

Layer 3 Network Monitoring...............................................................................................................................................................132

Browse IP Address.................................................................................................................................................................................132

IP Routing Table....................................................................................................................................................................................133

ARP Table...............................................................................................................................................................................................134

Browse Router Port ...............................................................................................................................................................................135

IP Mu lticast Forwarding Table..........................................................................................................................................................136

IGMP Group Table.................................................................................................................................................................................137

DVMRP Routing Table........................................................................................................................................................................138

Reboot and Factory Reset.......................................................................................................................................................................139

Web-Based Network Management...........................................................................................................................................................142

General Deployment Strategy.............................................................................................................................................................142

Assigning IP Network Addresses and Subnet Masks to VLANs...............................................................................................143

Defining Static Routes..........................................................................................................................................................................143

Getting Started..........................................................................................................................................................................................144

Configuring the Switch.............................................................................................................................................................................144

User Accounts Management ...............................................................................................................................................................144

Saving Changes......................................................................................................................................................................................146

Factory Reset..........................................................................................................................................................................................146

Using Web-Based Management............................................................................................................................................................147

Configuration.............................................................................................................................................................................................150

Switch IP Setup......................................................................................................................................................................................155

Switch Information................................................................................................................................................................................155

Power Supply & Cooling Fan Status.................................................................................................................................................156

Switch Settings ......................................................................................................................................................................................158

Configure Layer 3 - IP Networking.....................................................................................................................................................159

VLANs .....................................................................................................................................................................................................162

Priority.....................................................................................................................................................................................................172

Spanning Tree Protocol.........................................................................................................................................................................175

BOOTP/DHCP Relay .............................................................................................................................................................................185

Remote Management Setup...................................................................................................................................................................188

Management Station IP Settings ......................................................................................................................................................188

SNMP Community Settings ...............................................................................................................................................................189

Setup Trap Receivers............................................................................................................................................................................190

Setup User Accounts.............................................................................................................................................................................190

Serial Port Settings...............................................................................................................................................................................192

Network Monitoring.................................................................................................................................................................................193

Statistics ................................................................................................................................................................................................. 193

Address Table.........................................................................................................................................................................................197

Applications............................................................................................................................................................................................201

Maintenance...............................................................................................................................................................................................205

Upgrade Firmware from TFTP Server..............................................................................................................................................206

Download Configuration File from TFTP Server............................................................................................................................206

Upload Configuration File to TFTP Server......................................................................................................................................206

Save Log to TFTP Server......................................................................................................................................................................207

Restart System......................................................................................................................................................................................209

Technical Specific ations..............................................................................................................................................................................210

RJ-45 Pin Specification...............................................................................................................................................................................213

Runtime Switching Software Default Settings......................................................................................................................................214

Understanding and Troubleshooting the Spanning Tree Protocol.....................................................................................................215

Blocking State........................................................................................................................................................................................215

Listening State.......................................................................................................................................................................................216

Learning State........................................................................................................................................................................................217

Forwarding State...................................................................................................................................................................................217

Disabled State........................................................................................................................................................................................218

Troubleshooting STP................................................................................................................................................................................219

Spanning Tree Protocol Failure..........................................................................................................................................................219

Full/Half D uplex Mismatch.................................................................................................................................................................220

Unidirectional Link...............................................................................................................................................................................221

Packet Corruption..................................................................................................................................................................................221

Resource Errors ......................................................................................................................................................................................221

Identifying a Data Loop........................................................................................................................................................................222

Avoiding Trouble....................................................................................................................................................................................222

Brief Review of Bitwise Logical Operations ...........................................................................................................................................226

Index.................................................................................................................................................................................................................227

8-port Gigabit Ethernet Switch User’s Guide

A BOUT THIS GUIDE

This User’s guide tells you how to install your DGS -3308, how to connect it to your Ethernet network, and how to set its configuration using either the built-in console interface or Web-based management.

Overview of this User’s Guide

• Chapter 1, “Introduction.” Describes the Switch and its features.

• Chapter 2, “Unpacking and Setup.” Helps you get started with the basic installation of the Switch.

• Chapter 3, “Identifying External Components.” Describes the front panel, rear panel, and LED indicators of the

Switch.

• Chapter 4, “Connecting the Switch.” Tells how you can connect the Switch to your Ethernet network.

• Chapter 5, “Switch Management and Operating Concepts.” Talks about Local Console Management via the

RS-232 DCE console port and other aspects about how to manage the Switch.

• Chapter 6, “Using the Console Interface.” Tells how to use the built-in console interface to change, set, and monitor Switch performance and security.

• Chapter 7, “Web-Based Network Management.” Tells how to manage the Switch through an Internet browser.

• Appendix A, “Technical Specifications.” Lists the technical specifications of the DGS-3308TG and DGS-3308FG.

• Appendix B, “RJ-45 Pin Specifications.” Shows the details and pin assignments for the RJ-45

receptacle/connector.

• Appendix C, “Factory Default Settings.”

• Appendix D, “Understanding and Troubleshooting the Spanning Tree Protocol.”

• Appendix E, “Brief Review of Bitwise Logical Operations.”

8-port Gigabit Ethernet Switch User’s Guide

INTRODUCTION

This section describes the Layer 3 functionality and Layer 2 and Layer 3 features of the DGS-3308 Series switches. Some background information about Ethernet/Fast Ethernet, Gigabit Ethernet, and switching technology is presented. This is intended for readers who may not be familiar with the concepts of layered switching and routing but is not intended to be a complete or in -depth discussion.

For a more detailed discussion of the functionality of the DGS-3308, please see Chapter 5, “Switch Management and

Operating Concepts.”

Layer 3 Switching

Layer 3 switching is the integration of two proven technologies: switching and routing. In fact, Layer 3 switches are running the same routing routines and protocols as traditional routers. The main difference between traditional routing and Layer 3 switching is the addition of a group of Layer 2 switching domains and the execution of routing routines for most packets via an ASIC – in hardware instead of software.

Where a traditional router would have one, or at best a few, Fast Ethernet ports, the DGS-3308 Layer 3 switch has eight Gigabit Ethernet ports, including two which are GBIC-based. Where a traditional router would have one or two high-speed serial WAN connections, the DGS-3308 relies upon Gigabit Ethernet ports to connect to a separate device, which in turn, connects the network to a WAN or the Internet.

The DGS-3308 can be thought of as Fast Ethernet Layer 2 switc hing domains with a wire-speed router between each domain. It can be deployed in a network between a traditional router and the intranetwork. The traditional router and its associated WAN interface would then handle routing between the intranetwork and the WAN (the Internet, for example) while the Layer 3 switch would handle routing within the LAN (between the Fast Ethernet Layer 2 domains). Any installed Layer 2 switches, and indeed the entire subnetting scheme, would remain in place.

The DGS-3308FG can also replace key traditional routers for data centers and server farms, routing between these locations and the rest of the network, and providing eight ports of Layer 2 switching performance combined with wire-speed routing.

Backbone routers can also be replaced with DGS-3208FG and DGS-3208TG switches and a series of DGS-3308 switches could be linked via the Gigabit Ethernet ports. Routers that service WAN connections would remain in place, but would now be removed from the backbone and connected to the DGS-3308 via a Gigabit Ethernet port. The backbone itself could be migrated to Gigabit Ethernet, or faster technologies as they become available.

Policy services can then be introduced (or enhanced) in the backbone infrastructure and maintained throughout th e network – even to the desktop. With a distributed infrastructure and a logical management structure, network performance becomes easier to measure and fine-tune.

With the completion of the migration of the backbone to Gigabit or higher-performance technologies, the result is inherently scalable and easily evolved for future technologies. This core network will also become the termination point for Virtual Private Networks (VPNs) for remote office access to the enterprise infrastructure.

The DGS-3308 can then be thought of as accomplishing two objectives. First as a tool to provide high-performance access to enterprise data servers and infrastructure, and second, to enhance the performance of network equipment already

8-port Gigabit Ethernet Switch User’s Guide

installed. Many network segments display poor performance, but the Ethernet wire is only carrying a fraction of its total traffic capacity. The problem is not the network, but the ability of the connected devices to utilize the full capacity of the network. The DGS-3308 can eliminate network bottlenecks to high-traffic areas, and improve the utilization of the network’s installed bandwidth.

The Functions of a Layer 3 Switch

Traditional routers, once the core components of large networks, became an obstacle to the migration toward nextgeneration networks. Attempts to make software-based routers forward packets more quickly were inadequate.

A layer 3 switch does everything to a packet that a traditional router does:

• Determines forwarding path based on Layer 3 information

• Validates the integrity of the Layer 3 header via checksum

• Verifies packet expiration and updates accordingly

• Processes and responds to any optional information

• Updates forwarding statistics in the Management Information Base

• Applies security controls

A Layer 3 switch can be placed anywhere within a network core or backbone, easily and cost-effectively replacing the traditional collapsed backbone router. The DGS-3308 Layer 3 switch communicates with a WAN router using a standard Gigabit Ethernet or GBIC-based port. Multiple DGS-3308 switches can be linked via the Gigabit Ethernet ports.

Features

The DGS -3308 was designed for easy installation and high performance in an environment where traffic on the network and the number of users increase continuously.

Switch features include:

Ports

• Six 1000BASE-SX (SC-type fiber transceiver) for the DGS-3308FG or six 1000BASE-T (10/100/1000M Fast/Gigabit Ethernet) for the DGS-3308TG.

• Two GBIC-based Gigabit Ethernet ports.

• Fully compliant with IEEE 802.3z.

• Fully compliant with IEEE 802.3 10BASE-T, IEEE 802.3u 100BASE-TX, and IEEE 802.3ab 1000BASE-T (DGS -

3308TG only).

• Support Full Duplex operations.

• Supports auto-negotiation for 10M/100M/1000M speed (DGS-3308TG only).

• IEEE 802.3x compliant Flow Control support for full duplex.

• Supports Head of Line Blocking.

8-port Gigabit Ethernet Switch User’s Guide

• Per device packet buffer: 512Kbytes.

• RS-232 DCE Diagnostic port (console port) for setting up and managing the Switch via a connection to a console

terminal or PC using a terminal emulation program.

Performance Features

Layer 2 Switching Features

• 16 Gbps switching fabric capacity

• Wire speed packet forwarding rate per system.

• Store and forward switching scheme.

• Support 8K MAC address.

• Support Broadcast Storm control function.

• Support Port Mirroring.

• Port Trunking support for Gigabit Ethernet ports.

• 802.1D Spanning Tree support.

• 802.1Q Tagged VLAN support, including GVRP (GARP VLAN Registration Protocol) support for automatic VLAN

configuration distribu tion.

• 802.1p priority support (4 priority queues).

• Support IGMP Snooping.

Layer 3 Switching Features

• Wire speed IP forwarding.

• Hardware-based Layer 3 IP switching.

• IP packet forwarding rate up to 12 Mpps.

• 2K active IP address entry table per device.

• Supports RIP – (Routing Information Protocol) versions I and II.

• Support OSPF routing protocol.

• Supports IP version 4.

• IGMP version 1 and 2 support (RFC 1112 and RFC 2236).

• Supports PIM Dense Mode (draft-ietf-pim-v2-dm-03.txt).

• Supports DVMRP (draft-ietf-idmr-dvmrp-v3-09.txt).

• Supports IP multi-netting.

8-port Gigabit Ethernet Switch User’s Guide

• Supports IP packet de-fragmentation.

• Supports Path MTU discovery.

• Supports 802.1D frame support.

Traffic Classification and Prioritization

• Based on 802.1p priority bits.

• Based on MAC address.

• 4 priority queues.

Management

• RS-232 console port for out-of-band network management and system diagnosis via a console terminal or PC.

• Spanning Tree Algorithm Protocol for creation of alternative backup paths and prevention of network loops.

• SNMP v.1 Agent.

• Telnet remote control console.

• In-band control and configuration via SNMP based software.

• Flash memory for software upgrades. This can be done in -band via TFTP.

• Built-in SNMP management:

§ RFC 1213 MIB II.

§ RFC 1493 Bridge MIB.

§ RFC 1757 Four groups of RMON: Statistics, History, Alarm, and Event.

§ RFC 1724 RIP v2 MIB.

§ RFC 2737 Entity MIB.

§ RFC 2674 P-Bridge MIB.

§ RFC 2233 IF MIB.

§ RFC 2096 IP Forward MIB.

§ RFC 1907 SNMPv2 MIB

§ IGMP IGMP-STD MIB.

§ PIM MIB. This was extracted from draft-ief-idmr-pim-mib-03.txt.

§ DVMRP MIB. This was extracted from draft-thaler-dvmrp-mib-04.txt.

§ IPMROUTE MIB. This was extracted from draft-ietf-idmr-multicast-routmib-05.txt.

• Supports Web-based management.

• TFTP support.

8-port Gigabit Ethernet Switch User’s Guide

• BOOTP support.

• IP filtering on the management interface.

• DHCP Client support.

• DHCP Relay Agent.

• Password enabled.

Optional Redundant Power Supply

The DGS-3308FG supports the optional DPS-1000 (Redundant Power Supply) to provide automatic power supply monitoring and switchover to a redundant power supply (located in the chassis of the DPS-1000) in case of a failure in the Switch’s internal power supply. The DGS-3308TG does not support the optional redundant power supply.

Fast Ethernet Technology

100Mbps Fast Ethernet (or 100BASE -T) is a standard specified by the IEEE 802.3 LAN committee. It is an extension of the 10Mbps Ethernet standard with the ability to transmit and receive data at 100Mbps, while maintaining the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Ethernet protocol.

Gigabit Ethernet Technology

Gigabit Ethernet is an extension of IEEE 802.3 Ethernet utilizing the same packet structure, format, and support for CSMA/CD protocol, full duplex, flow control, and management objects, but with a tenfold increase in theoretical throughput over 100Mbps Fast Ethernet and a one hundred-fold increase over 10Mbps Ethernet. Since it is compatible with all 10Mbps and 100Mbps Ethernet environments, Gigabit Ethernet provides a straightforward upgrade without wasting a company’s existing investment in hardware, software, and trained personnel.

Gigabit Ethernet enables fast optical fiber connections and Unshielded Twisted Pair connections to support video conferencing, complex imaging, and similar data-intensive applications. Likewise, since data transfers occur 10 times faster than Fast Ethernet, servers outfitted with Gigabit Ethernet NIC’s are able to perform 10 times the number of operations in the same amount of time.

8-port Gigabit Ethernet Switch User’s Guide

U NPACKING AND SETUP

This chapter provides unpacking and setup information for the Switch.

Unpacking

Open the shipping carton of the Switch and carefully unpack its contents. The carton should contain the following items:

• One DGS-3308TG or DGS-3308FG 8-port Gigabit Ethernet Layer 3 Switch

• Mounting kit: 2 mounting brackets and screws

• Four rubber feet with adhesive backing

• One AC power cord

• One Installation Guide

• This User’s Guide on CD -ROM with Registration Card

If any item is found missing or damaged, please contact your local D -Link reseller for replacement.

Installation

Use the following guidelines when choosing a place to install the Switch:

• The surface must support at least 3 kg.

• The power outlet should be within 1.82 meters (6 feet) of the device.

• Visually inspect the power cord and see that it is secured to the AC power connector.

• Make sure that there is proper heat dissipation from and adequate ventilation around the switch. Do not place

heavy objects on the switch.

Desktop or Shelf Installation

When installing the Switch on a desktop or shelf, the rubber feet included with the device should first be attached. Attach these cushioning feet on the bottom at each corner of the device. Allow adequate space for ventilation between the device and the objects around it.

8-port Gigabit Ethernet Switch User’s Guide

Figure 2-1. Installing rubber feet for desktop installation

Rack Installation

The DGS -3308 can be mounted in an EIA standard-sized, 19-inch rack, which can be placed in a wiring closet with other equipment. To install, attach the mounting brackets on the Switch’s side panels (one on each side) and secure them with the screws provided.

Figure 2- 2A. Attaching the mounting brackets to the Switch

Then, use the screws provided with th e equipment rack to mount the switch on the rack.

8-port Gigabit Ethernet Switch User’s Guide

Figure 2-2B. Installing the Switch on an equipment rack

Power on

The DGS -3308 can be used with AC power supply 100 - 240 VAC, 50 - 60 Hz. The Switch’s power supply will adjust to the local power source automatically and may be powered on without having any or all LAN segment cables connected.

After the Switch is plugged in, the LED indicators should respond as follows:

• All LED indicators will momentarily blink. This blinking of the LED indicators represents a reset of the system.

• The Power LED indicator will blink while the Switch loads onboard software and performs a self-test. After

approximately 20 seconds, the LED will light again to indicate the switch is in a ready state.

• The Console LED indicator will remain ON if there is a connection at the RS-232 port, otherwise this LED indicator is OFF.

Power Failure

As a precaution in the event of a power failure, unplug the switch. When power is resumed, plug the Switch back in.

8-port Gigabit Ethernet Switch User’s Guide

IDENTIFYING E XTERNAL COMPONENTS

This chapter describes the front panel, rear panel, and LED indicators of the DGS-3308.

Front Panel

The front panel of the Switch consists of LED indicators, an RS-232 communication port, two GBIC-based Gigabit Ethernet ports, and either six 1000BASE -SX ports (DGS-3308FG) or six 1000BASE-T ports (DGS-3308-TG).

Figure 3-1a. Front panel view of the DGS-3308FG

Figure 3-1b. Front panel view of the DGS-3308TG

• Comprehensive LED indicators display the status of the Switch and the network (see the LED Indicators section below).

• An RS-232 DCE console port for setting up and managing the switch via a connection to a console terminal or PC using a terminal emulation program.

• Six Gigabit Ethernet ports (1000BASE -SX for DGS-3308FG and 1000BASE-T for DGS-3308TG).

• Two GBIC-based Gigabit Ethernet ports.

Rear Panel

The rear panel of the switch consists of a slot for the optional DPS-1000 (Redundant Power Supply) and an AC power connector.

Figure 3-2. Rear panel view of the Switch

8-port Gigabit Ethernet Switch User’s Guide

• The AC power connector is a standard three-pronged connector that supports the power cord. Plug-in the female connector of the provided power cord into this socket, and the male side of the cord into a power outlet. Supported input voltages range from 100 ~ 240 VAC at 50 ~ 60 Hz.

Side Panels

The right side panel of the Switch contains two system fans (see the top part of the diagram below). The left side panel contains heat vents.

Figure 3-3. Side panel views of the Switch

• The system fans are used to dissipate heat. The sides of the system also provide heat vents to serve the same purpose. Do not block these openings, and leave at least 6 inches of space at the rear and sides of the switch for proper ventilation. Be reminded that without proper heat dissipation and air circulation, system components might overheat, which could lead to system failure.

LED Indicators

The LED indicators of the Switch include Power, Console, Link/Act, and RPS In Use. The following shows the LED indicators for the Switch along with an explanation of each indicator.

• Power – This indicator on the front panel should be lit during the Power-On Self Test (POST). It will light green approximately 2 seconds after the Switch is powered on to indicate the ready state of the device.

• Console – This indicator is lit green when the Switch is being managed via out-of-band/local console management through the RS-232 console port using a straight-through serial cable.

• Link/Act – These indicators are located to the left and right of each port. They are lit when there is a secure connection (or link) to a device at any of the ports. The LEDs blink whenever there is reception or transmission (i.e. Activity--Act) of data occurring at a port.

• RPS in Use – This indicator is lit when the optional DPS-1000 Redundant Power Supply is being used.

8-port Gigabit Ethernet Switch User’s Guide

C ONNECTING THE SWITCH

This chapter describes how to connect the DGS-3308FG/DGS-3308TG to your Gigabit Ethernet network.

PC to Switch

A PC can be connected to the Switch via a four-pair Category 5 cable or a fiber optic cable. The PC should be connected to any of the eight ports of the DGS-3308FG/DGS-3308TG.

Figure 4-1. Switch connected to a PC or Workstation

The LED indicators for PC connection are dependent on the LAN card capabilities. If LED indicators are not illuminated after making a proper connection, check the PC’s LAN card, the cable, Switch conditions, and connections.

The following LED indicator state is possible for a PC to Switch connection:

• The Link/Act LED indicator lights up upon hooking up a PC that is powered on.

Switch to Switch (other devices)

The Switch can be connected to another switch or other devices (routers, bridges, etc.) via a fiber optic cable.

8-port Gigabit Ethernet Switch User’s Guide

Figure 4-2. Switch to switch connection

8-port Gigabit Ethernet Switch User’s Guide

S WITCH MANAGEMENT AND OPERATING

C ONCEPTS

This chapter discusses many of the concepts and features used to manage the switch, as well as the concepts necessary for the user to understand the functioning of the Switch. Further, this chapter explains many important points regarding these features.

Configuring the Switch to implement these concepts and make use of its many features is discussed in detail in the next chapters.

Some concepts are presented that are not currently implemented on the Switch. They are included to give a user who is unfamiliar with the concepts a brief overview of IP routing that is more complete – aid in the incorporation of the DGS 3308 in existing IP routed networks.

Local Console Management

A local console is a terminal or a workstation running a terminal emulation program that is connected directly to the switch via the RS-232 console port on the front of the switch. A console connection is referred to as an ‘Out -of-Band’ connection, meaning that console is connected to the switch using a different circuit than that used for normal network communications. So, the console can be used to set up and manage the switch even if the network is down.

Local console management uses the terminal connection to operate the console program built-in to the Switch (see Chapter 6, “Using the Console Interface”). A network administrator can manage, control and monitor the switch from the console program.

The DGS -3308 contains a CPU, memory for data storage, flash memory for configuration data, operational programs, and SNMP agent firmware. These components allow the Switch to be actively managed and monitored from either the console port or the network itself (out-of-band, or in -band).

Diagnostic (console) port (RS-232 DCE)

Out-of-band management requires connecting a terminal, such as a VT -100 or a PC running a terminal emulation program (such as HyperTerminal, which is automatically installed with Microsoft Windows) a to the RS-232 DCE console port of the Switch. Switch management using the RS-232 DCE console port is called Local Console Management to differentiate it from management performed via management platforms, such as D -View, HP OpenView, etc. Web-based Management describes management of the Switch performed over the network (in-band) using the switch’s built-in Web-based management program (see Chapter 7, “Web-based Network Management”). The operations to be performed and the facilities provided by these two built-in programs are identical.

The console port is set at the factory for the following configuration:

• Baud rate: 9,600

8-port Gigabit Ethernet Switch User’s Guide

• Data width: 8 bits

• Parity: none

• Stop bits: 1

• Flow Control None

Make sure the terminal or PC you are using to make this connection is configured to match these settings. If you are having problems making this connection on a PC, make sure the emulation is set to VT -100. If you still don’t

see anything, try hitting <Ctrl> + r to refresh the screen.

IP Addresses and SNMP Community Names

Each Switch must be assigned its own IP Address, which is used for communication with an SNMP netwo rk manager or other TCP/IP application (for example BOOTP, TFTP). The Switch’s default IP address is 10.90.90.90. You can change the default Switch IP Address to meet the specification of your networking address scheme.

The Switch is also assigned a unique MAC address by the factory. This MAC address cannot be changed, and can be found from the initial boot console screen – shown below.

Figure 5-1. Boot screen

The Switch’s MAC address can also be found from the console program under the Switch Information menu item, as shown below.

8-port Gigabit Ethernet Switch User’s Guide

Figure 5-2. Switch Information screen

In addition, you can also set an IP Address for a gateway router. This becomes necessary when the network management station is located on a different IP network from the Switch, making it necessary for management packets to go through a router to reach the network manager, and vice-versa.

For security, you can set in the Switch a list of IP Addresses of the netw ork managers that you allow to manage the Switch. You can also change the default SNMP Community Strings in the Switch and set the access rights of these Community Strings. In addition, a VLAN may be designated as a Management VLAN.

Traps

Note: Traps are messages that alert you of events that occur on the Switch. The events can be as

serious as a reboot (someone accidentally turned OFF the Switch), or less serious like a port status change. The Switch generates traps and sends them to the network manager (trap recipient).

Trap recipients are special users of the network who are given certain rights and access in overseeing the maintenance of the network. Trap recipients will receive traps sent from the Switch; they must immediately take certain actions to avoid future failure or breakdown of the network.

You can also specify which network managers may receive traps from the Switch by entering a list of the IP addresses of authorized network managers. Up to four trap recipient IP addresses, and four corresponding SNMP community strings can be entered.

Note: SNMP community strings function like passwords in that the community string entered for a

given IP address must be used in the management station software, or a trap will be sent.

The following are trap types the Switch can send to a trap recipient:

8-port Gigabit Ethernet Switch User’s Guide

• Cold Start – This trap signifies that the Switch has been powered up and initialized such that software settings are reconfigured and hardware systems are rebooted. A cold start is different from a factory reset in that configuration settings saved to non-volatile RAM used to reconfigure the switch.

• Warm Start – This trap signifies that the Switch has been rebooted, however the POST (Power On Self-Test) is skipped.

• Authentication Failure – This trap signifies that someone has tried to logon to the switch using an invalid SNMP community string. The Switch automatically stores the source IP address of the unauthorized user.

• New Root – This trap indicates that the Switch has become the new root of the Spanning Tree, the trap is sent by the switch soon after its election as the new root. This implies that upon expiration of the Topology Change Timer the new root trap is sent out immediately after the Switch’s election as the new root.

• Topology Change (STP) – A Topology Change trap is sent by the Switch when any of its configured ports transitions from the Learning state to the Forwarding state, or from the Forwarding state to the Blocking state. The trap is not sent if a new root trap is sent for the same transition.

• New Root (STP) – A New Root trap is sent be the switch whenever a new root port is elected within an STP group.

• Link Up – This trap is sent whenever the link of a port changes from link down to link up.

• Link Down – This trap is sent whenever the link of a port changes from link up to link down.

MIBs

Management and counter information are stored in the Switch in the Management Information Base (MIB). The Switch uses the standard MIB -II Management Information Base module. Consequently, values for MIB objects can be retrieved from any SNMP-based network management software. In addition to the standard MIB -II, the Switch also supports its own proprietary enterprise MIB as an extended Management Information Base. These MIBs may also be retrieved by specifying the MIB’s Object-Identity (OID) at the network manager. MIB values can be either read-only or read-write.

Read-only MIBs variables can be either constants that are programmed into the Switch, or variables that change while the Switch is in operation. Examples of read-only constants are the number of port and type of ports. Examples of read-only variables are the statistics counters such as the number of errors that have occurred, or how many kilobytes of data have been received and forwarded through a port.

Read-write MIBs are variables usually related to user-customized configurations. Examples of these are the Switch’s IP Address, Spanning Tree Algorithm parameters, and port status.

If you use a third-party vendors’ SNMP software to manage the Switch, a diskette listing the Switch’s propriety enterprise MIBs can be obtained by request. If your software provides functions to browse or modify MIBs, you can also get the MIB values and change them (if the MIBs’ attributes permit the write operation). This process however can be quite involved, since you must know the MIB OIDs and retrieve them one by one.

SNMP

Simple Network Management Protocol (SNMP) is an OSI layer 7 (the application layer) protocol for remotely monitoring and configuring network devices. SNMP enables network management stations to read and modify the settings of gateways, routers, switches, and other network devices. SNMP can be used to perform many of the same functions as a directly connected console, or can be used within an integrated network management software package such as DView.

The Switch has a software program called an ‘agent’ that processes SNMP requests, but the user program that makes the requests and collects the responses runs on a management station (a designated computer on the network). The SNMP agent and the user program both use the UDP/IP protocol to exchange packets.

8-port Gigabit Ethernet Switch User’s Guide

Authentication

The authentication protocol ensures that both the router SNMP agent and the remote user SNMP application program discard packets from unauthorized users. Authentication is accomplished using ‘community strings’, which function like passwords. The remote user SNMP application and the router SNMP must use the same community string. SNMP community strings of up to 20 characters may be entered under the Remote Management Setup menu of the console program.

Packet Forwarding

The Switch enters the relationship between destination MAC or IP addresses and the Ethernet port or gateway router the destination resides on into its forwarding table. This information is then used to forward packets. This reduces the traffic congestion on the network, because packets, instead of being transmitted to all ports, are transmitted to the destination port only. Example: if Port 1 receives a packet destined for a station on Port 2, the Switch transmits that packet through Port 2 only, and transmits nothing through the other ports. This process is referred to as ‘learning’ the network topology.

MAC Address Aging Time

The Aging Time affects the learning process of the Switch. Dynamic forwarding table entries, which are made up of the source and destination MAC addresses and their associated port numbers, are deleted from the table if they are not accessed within the aging time.

The aging time can be from 10 to 1,000,000 seconds with a default value of 300 seconds. A very long aging time can result in dynamic forwarding table entries that are out -of-date or no longer exist. This may cause incorrect packet forwarding decisions by the Switch.

If the Aging Time is too short however, many entries may be aged out too soon. This will result in a high percentage of received packets whose source addresses cannot be found in the forwarding table, in which case the switch will broadcast the packet to all ports, negating many of the benefits of having a switch.

Static forwardin g entries are not affected by the aging time.

Filtering

The Switch uses a filtering database to segment the network and control communication between segments. It can also filter packets off the network for intrusion control. Static filtering entries can be made by MAC Address or IP Address filtering.

Each port on the Switch is a unique collision domain and the switch filters (discards) packets whose destination lies on the same port as where it originated. his keeps local packets from disrupting communications on other parts of the network.

For intrusion control, whenever a switch encounters a packet originating from or destined to a MAC address or an IP Address entered into the filter table, the switch will discard the packet.

Some filte ring is done automatically by the switch:

• Dynamic filtering – automatic learning and aging of MAC addresses and their location on the network. Filtering occurs to keep local traffic confined to its segment.

• Filtering done by the Spanning Tree Protocol, which can filter packets based on topology, making sure that signal loops don’t occur.

• Filtering done for VLAN integrity. Packets from a member of a VLAN (VLAN 2, for example) destined for a device on another VLAN (VLAN 3) will be filtered.

8-port Gigabit Ethernet Switch User’s Guide

Some filtering requires the manual entry of information into a filtering table:

• MAC address filtering – the manual entry of specific MAC addresses to be filtered from the network. Packets sent from one manually entered MAC address can be filtered from the network. The entry may be specified as either a source, a destination, or both.

• IP address filtering – the manual entry of specific IP addresses to be filtered from the network (switch must be in IP Routing mode). Packets sent from one manually entered IP address to another can be filtered from the network. The entry may specified as either a source, a destination, or both (switch must be in IP Routing mode).

IP Addressing and Subnetting

This section gives basic information needed to configure your Layer 3 switch for IP routing. The information includes how IP addresses are broken down and how subnetting works. You will learn how to assign each interface on the router an IP address with a unique subnet.

Definitions

• IP Address – the unique number ID assigned to each host or interface on a network. IP addresses have the form xxx.xxx.xxx.xxx.

• Subnet – a portion of a network sharing a particular network address.

• Subnet mask – a 32-bit number used to describe which portion of a Network Address refers to the subnet and

which portion refers to the host. Subnet masks have the form xxx.xxx.xxx.xxx.

• Interface – a network connection

• IP Interface – another name for subnet.

• Network Address – the resulting 32-bit number from a bitwise logical AND operation performed between an

IP address and a subnet mask.

• Subnet Address – another name for network address.

Note: In a subnetted network, all addresses consist of two parts: an IP address and a subnet mask. The two are

used together and one is meaningless without the other.

IP Addresses

The Internet Protocol (IP) was designed for routing data between network sites. Later, it was adapted for routing between networks (referred to as “subnets”) within a site. The IP defines a way of generating an unique number that can be assigned each network in the internet and each of the computers on each of those networks. This number is called the IP address.

IP addresses use a “dotted decimal” notation. Here are some examples of IP addresses written in this format:

1. 210.202.204.205

2. 189.21.241.56

3. 125.87.0.1

This allows IP address to be written in a string of 4 decimal (base 10) numbers. Computers can only understand binary (base 2) numbers, and these binary numbers are usually grouped together in bytes, or eight bits. (A bit is a binary digit – either a “1” or a “0”). The dots (periods) simply make the IP address easier to read. A computer sees an IP address not as four decimal numbers, but as a long string of binary digits (32 binary digits or 32 bits, IP addresses are 32-bit addresses).

The three IP addresses in the example above, written in binary form are:

1. 11010010.11001010.11001100.11001101

2. 10111101.00010101.11110001.00111000

3. 01111101.01010111.00000000.00000001

The dots are included to make the numbers easier to read.

8-port Gigabit Ethernet Switch User’s Guide

Eight binary bits are called a ‘byte’ or an ‘octet’. An octet can represent any decimal value between ‘0’ (00000000) and ‘255’ (11111111). IP addresses, represented in decimal form, are four numbers whose value is between ‘0’ to ‘255’. The total range of IP addresses are then:

Lowest possible IP address - 0.0.0.0 Highest possible IP address - 255.255.255.255

To convert decimal numbers to 8-bit binary numbers (and vice-versa), you can use the following chart:

Binary Octet Digit 27 26 25 24 23 22 21 2

Decimal Equivalent 128 64 32 16 8 4 2 1

Binary Number

128+64+32+16+8+4+2+1=

255

1 1 1 1 1 1 1 1

Table 5-1. Binary to Decimal Conversion

Each digit in an 8-bit binary number (an octet) represents a power of two. The left-most digit represents 2 raised to the 7th power (2x2x2x2x2x2x2=128) while the right -most digit represents 2 raised to the 0th power (any number raised to the 0th power is equal to one, by definition).

IP addresses actually consist of two parts, one identifying the network and one identifying the destination (node) within the network. The IP address discussed above is one part and a second number called the Subnet mask is the other part. To make this a bit more confusing, the subnet mask has the same numerical form as and IP address.

Address Classes

Address classes refer to the range of numbers in the subnet mask. Grouping the subnet masks into classes makes the task of dividing a network into subnets a bit easier.

There are 5 address classes. The first 4 bits in the IP address determine which class the IP address falls in.

• Class A addresses begin with 0xxx, or 1 to 126 decimal.

• Class B addresses begin with 10xx, or 128 to 191 decimal.

• Class C addresses begin with 110x, or 192 to 223 decimal.

• Class D addresses begin with 1110, or 224 to 239 decimal.

• Class E addresses begin with 1111, or 240 to 254 decimal.

Addresses beginning with 01111111, or 127 decimal, are reserved. They are used for internal testing on a local machine (called loopback). The address 127.0.0.1 can always be pinged from a local node because it forms a loopback and points back to the same node.

Class D addresses are reserved for multicasting. Class E Addresses are reserved for future use. They are not used for node addresses. The part of the IP address that belongs to the network is the part that is ‘hidden’ by the ‘1’s in the subnet mask. This can

be seen below:

• Class A NETWORK.node.node.node

• Class B NETWORK.NETWORK.node.node

• Class C NETWORK.NETWORK.NETWORK.node

For example, the IP address 10.42.73.210 is a Class A address, so the Network part of the address (called the Network Address) is the first octet (10.x.x.x). The node part of the address is the last three octets (x.42.73.210).

To specify the network address for a given IP address, the node part is set to all “0”s. In our example, 10.0.0.0 specifies the network address for 10.42.73.210. When the node part is set to all “1”s, the address specifies a broadcast address. So,

10.255.255.255 is the broadcast address for the network 10.0.0.0.

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