3COM CS 2500 User Manual

Download

LAN

WITCHING

PLEX

2500 E

SER

XTENDED

UIDE

Part No. 801-00343-000 Published November 1996 Revision 02

3Com Corporation

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© 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 Unpublished rights reserved under the copyright laws of the United States.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.

ONTENTS

BOUT

HIS

UIDE

Introduction 1 How to Use This Guide 1 Conventions 2 LANplex 2500 Documentation 3 Documentation Comments 5

ART

II V

ETTING

LAN

About LANplex Extended Switching 1-1 Using Menus 1-2

IRTUAL

VLAN

About VLANs 2-1

TARTED

PLEX

® E

XTENDED

Bridge Menu 1-3 IP Menu 1-4 IPX Menu 1-5 Appletalk Menu 1-6

LAN T

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

WITCHING

ECHNOLOGY

PLEX

® S

YSTEM

EATURES

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

OUTING

ROTOCOLS

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

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

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

THE

ECHNOLOGY

LAN

PLEX

® S

YSTEM

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

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

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

Named Entities 7-2

Transport Layer Protocols 7-6 The Session Layer Protocols 7-9

PPLE

ALK

® E

NVIRONMENT

ART

IV A

Displaying VLAN Information 8-1 Deﬁning VLAN Information 8-3 Modifying VLAN Information 8-4 Removing VLAN Information 8-5

Administering interfaces 9-1

Administering Routes 9-9

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

VLAN

IP R

OUTING

XTENDED

WITCHING

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

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

OUTING

Displaying Routes 10-8 Displaying the Multicast Cache 10-9

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

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

PPLE

ALK

® R

OUTING

ART

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

ONITORING

(RMON)

AND

THE

ART

LAN

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

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

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

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

statistics menu

ddp rtmp zip nbp

Figure 1-4 Appletalk Menu Hierarchy

VLANS ON THE

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.

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

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.

About VLANs 2-9

If layer 3 information is provided in the IP VLAN for which you are conﬁguring an IP interface, the subnet portion of both addresses must be compatible.

For example:

IP VLAN subnet 157.103.54.0 with subnet mask of 255.255.255.0 IP host interface address 157.103.54.254 with subnet mask of

255.255.255.0

Layer 2 (bridging) communication is still possible within an IP VLAN (or router interface) for the group of ports within that IP Inter face’s IP VLAN. IP data destined for a different IP subnet uses the IP routing interface to get to that different subnet, even if the destination subnet is on a shared port.

2-10 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM

VLAN Examples Example 1

Figure 2-1 is an example of a simple conﬁguration that contains three protocol-sensitive VLANs (2 IP and 1 IPX) that share a high-speed FDDI link. The end-stations and servers are on 10Mbps ports with trafﬁc segregated by protocol. They are only aggregated over the high-speed FDDI link. See .

IP-1 IP-2 IPX-1

LANplex 2500

IP-1 VLAN #1

Power Run

ERROR PCMCIA

Processor Power

Config Inserted

Fan Temp

IP-2 VLAN #2

FDDI

Modem Terminal

IPX-1 VLAN #3

LANplex 2500

Power Run

IP-1 IP-2 IPX-1

ERROR PCMCIA

Processor Power

Config Inserted

Fan Temp

IP-1 Server

Modem Terminal

IPX-1 Server

IP-2 Server

Figure 2-1 Example of a Protocol-Sensitive VLAN Conﬁguration

About VLANs 2-11

Example 2

Figure 2-2 is an example of a conﬁguration that contains two different protocol-sensitive VLANs (IP and IPX) with servers on separate high-speed 100BASE-T ports. The end-station clients share the same switch ports, yet the IP and IPX trafﬁc stays separate. See Figure 2-2.

= VLAN 1 (IP)

IP Server VLAN #1

= VLAN 2 (IPX)

= VLAN 1 (IP) + VLAN 2 (IPX)

Fast Ethernet 100 BASEt

IP Server VLAN #1, #2, and #3

LANplex 2500

Power Run

ERROR PCMCIA

Process Power

Config Inserted

Fan Temp

IP IP

Modem Terminal

IPX Server VLAN #2

Figure 2-2 A VLAN Conﬁguration with Servers on Separate 100BASE-T ports.

IPX

2-12 CHAPTER 2: VLANS ON THE LANPLEX® SYSTEM

BRIDGING AND ROUTING IN THE

What Is Routing? Routing is the process of distributing packets over potentially dissimilar

LAN

This chapter shows how the LANplex® system operates in a subnetworked routing environment and describes the LANplex routing methodology — speciﬁcally, how the LANplex bridging and routing model compares with traditional models.

networks. A router (also called a gateway) is the machine that accomplishes this task. Routers are typically used to:

■ Connect enterprise networks together

■ Connect subnetworks (or client/server networks) to the enterprise network

Figure 3-1 shows where routers are typically used in a network. The LANplex system performs routing that connects subnets to the

enterprise network, providing connectivity between devices within a workgroup, depar tment, or building.

PLEX

SYSTEM

3-2 CHAPTER 3: BRIDGING AND ROUTING IN THE LANPLEX® SYSTEM

Connecting enterprise networks

Sales

Router

LANplex in a

Subnetworked

Environment

Router

FDDI Backbone

Router

Bridge Bridge Bridge Bridge

Engineering

Figure 3-1 Traditional Architecture of a Routed Network

The LANplex system allows you to ﬁt Ethernet switching capability into highly subnetworked environments. When you put the LANplex system into such a network, the system streamlines your network architecture and easily switches trafﬁc between and within subnets over Ethernet and FDDI. See Figure 3-2.

Router

Connecting subnets to the enterprise

Marketing

Bridge

Sales

Router

FDDI backbone

LANplex®

Engineering

LANplex®

Figure 3-2 Subnetted Architecture with LANplex® Switching Hubs

Marketing

What Is Routing? 3-3

Integrating

Bridging and

Routing

Subnet 1

The LANplex system integrates bridging and routing. Multiple switch ports can be assigned to each subnet. See Figure 3-3. Trafﬁc between ports assigned to the same subnet is switched transparently using transparent bridging or Express switching (described in the LANplex® 2500 Operation Guide). Trafﬁc traveling to different subnets is routed using one of the supported routing protocols.

In the following descriptions of bridging and routing on the LANplex system, the term MAC address refers to a physical hardware address. The term network address refers to a logical address that applies to a speciﬁc protocol.

Subnet 4

LANplex 2500

FDDI ports

Ethernet ports

Subnet 3

Subnet 2

Figure 3-3 Multiple Ports per Subnets with the LANplex 2500 System

Because the LANplex model of bridging and routing allows several segments to be connected to the same subnet, you can increase the level of segmentation in your network without having to create new subnets or assign network addresses. Instead, you can use additional Ethernet ports to expand your existing subnets. This is in contrast to more traditional forms of bridging and routing where, at most, one port is connected to any subnet.

3-4 CHAPTER 3: BRIDGING AND ROUTING IN THE LANPLEX® SYSTEM

In the traditional model, if you want to increase the level of segmentation in your network, you must create additional subnets and assign new network addresses to your existing hosts.

Bridging and Routing Models

Traditional Bridging

and Routing Model

The way routing is implemented in the LANplex system differs from how bridging and routing usually coexist in a system.

■ Traditional Bridging and Routing Model — Traditionally, bridging and

routing are peer entities; either a packet is bridged or routed. Packets belonging to recognized protocols are routed; all others are bridged.

■ LANplex Bridging and Routing Model — In the LANplex model, the

bridge and router operate hierarchically on the LANplex system, routing over bridging. When a packet enters the system, the system ﬁrst tries to bridge the packet. If the packet’s destination network address is not on the same subnet, then the system routes the packet.

The bridge or router determines whether a packet should be bridged or routed based on the protocol to which the packet belongs. If the packet belongs to a recognized protocol, the packet is routed. O therwise, it is bridged.

In the traditional bridging and routing model, a packet is bridged as follows (see Figure 3-4):

1 The packet enters the bridge or router. 2 The bridge or router determines that the packet does not belong to a

recognized routing protocol, so the packet is passed to the bridge.

3 The bridge examines the destination MAC address and forwards the

packet to the port on which that address has been learned.

Bridging and Routing Models 3-5

Router Bridge

Transmitting host

Router vs. Bridge ?

Interfaces (ports)

Networks

Destination host

Figure 3-4 Bridging in the Traditional Bridging and Routing Model

In the traditional bridging and routing model, a packet is routed as follows (see Figure 3-5):

1 The packet enters the bridge or router. 2 The bridge or router determines that the packet belongs to a

recognized routing protocol, so the packet is passed to the router.

3 The router examines the destination network address and forwards the

packet to the interface (por t) connected to the destination subnet.

Router

Bridge

Transmitting host

Router vs. Bridge ?

Destination host

Figure 3-5 Routing in the Traditional Bridging and Routing Model

Interfaces (ports) Networks

3-6 CHAPTER 3: BRIDGING AND ROUTING IN THE LANPLEX® SYSTEM

LANplex Bridging

and Routing Model

The LANplex 2500 system uses the destination MAC address to determine whether it will bridge or route a packet. Before a host system sends a packet to another host, it compares its own network address to the network address of the other host as follows:

■ If network addresses are on the same subnet, the packet is bridged

directly to the destination host’s address.

■ If network addresses are on different subnets, the pack et must be

routed from one subnet to the other. In this case, the host transmits the packet to the connecting router’s MAC address.

In the LANplex bridging/routing model, a packet is bridged as follows (see Figure 3-6):

1 The packet enters the LANplex system. 2 The packet’s destination MAC address is examined by the bridging layer. 3 The destination MAC address does not correspond to the MAC address

of one of the system ports conﬁgured for routing. The bridging layer selects a segment (port) based on the destination MAC address and forwards the packet to that segment.

Router

123

Transmitting Host

Destination Host

Bridge

Figure 3-6 Bridging in the LANplex Bridging and Routing Model

Routing Layer

Router Interfaces

Bridging Layer

Subnets

Bridging and Routing Models 3-7

In the LANplex bridging and routing model, a packet is routed as follows (see Figure 3-7):

1 The packet enters the LANplex system. 2 The packet’s destination address is examined by the bridging layer. 3 The destination address corresponds to the address of one of the system

ports conﬁgured for routing (as opposed to a learned end-station address). The packet is passed to the router interface associated with the port on which the packet was received.

4 The routing layer:

a Selects a destination inter face based on the destination network

address.

b D etermines the MAC address of the next hop (either the destination

host or another gateway).

c Passes the packet back to the bridging layer.

5 The bridging layer then selects a segment (port) based on the destination

MAC address and forwards the packet to that segment.

Transmitting Host

123

Destination Host

Figure 3-7 Routing in the LANplex Bridging and Routing Model

Router

Bridge

Routing Layer

Router Interfaces

Bridging Layer

Subnets

3-8 CHAPTER 3: BRIDGING AND ROUTING IN THE LANPLEX® SYSTEM

ROUTING WITH IP TECHNOLOGY

This chapter gives an overview of IP routing technology, speciﬁcally deﬁning:

■ What IP routing involves

■ What elements are necessary for IP routers to effectively transmit packets

■ How IP routing transmission errors are detected and resolved

■ Routing with classical IP over ATM

IP Routing and the OSI Model

An IP router, unlike a bridge, operates at the network layer of the OSI Reference Model. That is, it routes packets by examining the network layer address (IP address). Bridges use the data-link layer MAC addresses to make forwarding decisions. See Figure 4-1.

OSI Reference Model

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data-link Layer

Physical Layer

Figure 4-1 OSI Reference Model and IP Routing

ARP

MAC

RIP

ICMP

4-2 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

When an IP router sends a packet, it does not know the complete path to a destination — only the next hop. Each hop involves three steps:

■ The IP routing algorithm computes the next hop IP address, and next

router interface, using the routing table entries.

■ The Address Resolution Protocol (ARP) translates the next hop IP

address into a physical MAC address.

■ The router sends the packet over the network to the next hop.

These routing elements are described in more detail in the following section.

Elements of IP Routing

IP Addresses IP addresses are 32-bit addresses composed of a network part (the

IP routers use the following elements to transmit packets in a subnetworking environment:

■ IP addresses

■ Router interfaces

■ Routing tables

■ Address Resolution Protocol (ARP)

address of the network on which the host is located) and a host part (the address of the host on that network). See Figure 4-2. IP addresses differ from Ethernet and FDDI MAC addresses, which are unique hardware-conﬁgured 48-bit addresses.

IP Address

network host

The boundary between

network and host parts

depends on the

class

of IP

Figure 4-2 IP Address: Network Part and Host Part

32 bits

A central agency assigns the network part of the IP address, and the network administrator assigns the host part. All devices connected to the same network share the same IP address preﬁx (the network part of the address).

Elements of IP Routing 4-3

Address Classes

The boundary of the network part and the host par t depends on the class that the central agency assigns to your network. The primary classes of IP addresses are Class A, Class B, and Class C.

■ Class A addresses — have 8 bits for the network part and 24 bits for

the host part. Although only a few Class A networks can be created, each can contain a very large number of hosts.

■ Class B addresses — have 16 bits for the network part and 16 bits for

the host part.

■ Class C addresses — have 24 bits for the network part and eight bits

for the host part. Each Class C network can contain only up to 254 hosts, but many such networks can be created.

The class of an IP address is designated in the high-order bits of the network parts of the address.

Subnet Part of an IP Address

In some environments, the IP address contains a subnet part. Subnetting allows a single Class A, B, or C network to be further subdivided internally while still appearing as a single network to other networks. The subnet part of the IP address is only visible to those hosts and gateways on the subnet network.

When an IP address contains a subnet part, a subnet mask is used to identify which bits are the subnet address and which are the host address. A subnet mask is a 32-bit number that uses the same format and representation as IP addresses. Each IP address bit corresponding to a 1 in the subnet mask is in the network or subnet part of the address. Each IP address bit corresponding to a 0 is in the host part of the IP address. See Figure 4-3.

4-4 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

Take the IP address

IP Address

Subnet Mask

Network

Apply the subnet mask

101111111111 00000001111111111111

Result = subnet/host boundary

networ

Network

Subnet and Host

Subnet

subn

Host

Figure 4-3 How a Subnet Mask Is Applied to the IP Address

An example of an IP address that includes network, subnet, and host parts is 158.101.230.52 with a subnet mask of 255.255.255.0. This address is divided as follows:

■ 158.101 is the network part

■ 230 is the subnet part

■ 52 is the host part

Router Interfaces A router inter face is the connection between the router and a subnet.

In traditional routing models, the interface is the same as the port, since only one interface can exist per port. In the LANplex system’s IP routing model, more than one port can be connected to the same subnet.

Each router interface has an IP address and a subnet mask. This address deﬁnes both the number of the network to which the router interface is attached and its host number on that network. A router interface’s IP address serves two functions:

■ The IP address is used when sending IP packets to or from the router

itself.

■ The IP address deﬁnes the network and subnet numbers of the

segment connected to that interface. See Figure 4-4.

Elements of IP Routing 4-5

Network 2

Network 1

Interfaces

158.101.1.2 158.101.2.2 12

158.101.2.1

Router

Interface 1 IP Address

158.101.1.1

Interface

158.101.3.2

158.101.3.1

Network 3

Figure 4-4 Router Interfaces in the LANplex System

Routing Table A routing table allows a router or host to determine how to send a

packet toward the packet’s ultimate destination. The routing table contains an entry for every destination network, subnet, or host to which the router or host is capable of forwarding packets. A router or host uses the routing table when the destination IP address of the packet it is sending is not on a network or subnet to which it is directly connected. The routing table provides the IP address of a router that can forward the packet toward its destination.

The routing table consists of the following elements:

■ Destination IP Address — the destination network, subnet, or host

■ Subnet Mask — the subnet mask corresponding to the destination IP

address

■ Metric — a measure of the “distance” to the destination. In the Routing

Information Protocol (RIP), the metric is the number of hops.

■ Gateway — the IP address of the next hop router (the IP address of the

interface through which the packet travels)

■ Interface — the interface number through which a packet must travel

to reach that router Figure 4-5 shows the routing table of the router in Figure 4-4.

4-6 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

Routing T able

Destination IP Address Interface

158.101.1.1

158.101.2.1

158.101.3.1 default route

Subnet Mask

255.255.255.0

Metric

1 1 1 1

Gateway

158.101.1.2

158.101.2.2

158.101.3.2

158.101.1.2

1 2 3 1

Figure 4-5 Example of a Routing Table in the LANplex Routing Model

Routing table information is generated and updated in either of the following ways:

■ Statically — You manually enter routes, which do not change until

you change them (that is, they will not time out).

■ Dynamically — The router uses a routing protocol, such as RIP, to

exchange information. Routes are recalculated at regular intervals.

Static Routes

A static route is one that you manually conﬁgure in the routing table. Static routes are useful in environments where no routing protocol is used or where you want to override some of the routes generated with a routing protocol. Because static routes do not automatically change in response to network topology changes, you should manually conﬁgure only a small number of reasonably stable routes.

Dynamic Routes Using RIP

Automated methods of conﬁguring routes help you keep up with a changing network environment, allowing routes to be reconﬁgured quickly and reliably. Interior Gateway Protocols (IGP), which operate within networks, provide this automated method. The LANplex system uses the Routing Information Protocol (RIP), one of the most widely used IGPs, to conﬁgure its routing tables dynamically.

RIP operates in terms of active and passive devices. The active devices, usually routers, broadcast their RIP messages to all devices in a network or subnet; they update their own routing tables when they receive a RIP message. The passive devices, usually hosts, listen for RIP messages and update their routing tables; they do not send RIP messages.

Elements of IP Routing 4-7

An active router sends a RIP message every 30 seconds. This message contains both the IP address and a metric (the distance to the destination from that router) for each destination. In RIP, each router that a packet must travel through to reach a destination equals one hop.

Default Route

In addition to the routes to speciﬁc destinations, the routing table may contain an entry called the default route. The router uses the default route to forward packets that do not match any other routing table entry. A default route is often used in place of routes to numerous destinations all having the same gateway IP address and interface number. The default route can be conﬁgured statically, or it can be learned dynamically using RIP.

Address Resolution

Protocol (ARP)

ARP is a low-level protocol used to locate the MAC address corresponding to a given IP address. This protocol allows a host or router to make its routing decisions using IP addresses while it uses MAC addresses to forward packets from one hop to the next.

Once the host or router knows the IP address of the next hop to the destination, the host or router must translate that IP address into a MAC address before the packet can be sent. To do this translation, the host or router ﬁrst looks in its ARP cache, a table of IP addresses with their corresponding MAC addresses. Each device par ticipating in IP routing maintains an ARP cache. See Figure 4-6.

ARP Cache

IP Address MAC Address

158.101.1.1

158.101.2.1

Figure 4-6 Example of an ARP Cache

00308e3d0042 0080232b00ab

If the IP address does not have a corresponding MAC address listed, the host or router broadcasts an ARP request packet to all the devices on the network. The ARP request contains information about the hardware and

4-8 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

protocol. The two key elements of the ARP request are the target and source addresses for both the hardware (MAC addresses) and the protocol (IP addresses). See Figure 4-7.

ARP Request

00802322b00ad

158.101.2.1 ?

158.101.2.15

Source hardware address Source protocol address Target hardware address Target protocol address

Figure 4-7 Example of an ARP Request Packet

When the devices on the network receive this packet, they examine it, and if their address is not the target protocol address, they discard the packet. When a device receives the packet and conﬁrms that its IP address matches the target protocol address, this device places its MAC address in the target hardware address ﬁeld and sends the packet back to the source hardware address. When the originating host or router receives the ARP reply, it places the new MAC address in its ARP cache next to the corresponding IP address. See Figure 4-8.

ARP Cache

IP Address MAC Address

158.101.1.1

158.101.2.1

158.101.3.1

00308e3d0042 0080232b00ab 0134650f3000

Figure 4-8 Example of ARP Cache Updated with ARP Reply

Once the MAC address is known, the host or router can send the packet directly to the next hop.

IP Routing Transmission Errors 4-9

IP Routing Transmission Errors

Because each router only knows about the next hop, it is not aware of problems that might be further “down the road” toward the destination. Destinations can be unreachable if:

■ Hardware is temporarily out of service

■ You inadvertently speciﬁed a nonexistent destination address

■ The router does not have a route to the destination network

To help routers and hosts know of problems in packet transmission, an error-reporting mechanism called Internet Control Message Protocol (ICMP) provides error reporting back to the source when routing problems arise. ICMP allows you to determine whether a delivery failure resulted from a local or a remote malfunction.

ICMP does the following:

■ Tests the reachability of nodes (ICMP Echo Request and ICMP Echo Reply)

A host or gateway sends an ICMP echo request to a speciﬁed destination. If the destination receives the echo request, it sends an ICMP echo reply back to the original sender. This process tests whether the destination is reachable and responding and veriﬁes that the major pieces of the transport system work. The ping command is one frequently used way to invoke this process.

■ Creates more efﬁcient routing (ICMP Redirect)

Often the host route conﬁguration speciﬁes the minimal possible routing information needed to communicate (for example, the address of a single router). The host relies on routers to update its routing table. In the process of routing packets, a router may detect a host not using the best route. The router then sends the host an ICMP redirect, requesting that the host use a different gateway when sending packets to that destination. The next time the host sends a packet to that same destination, it uses the new route.

■ Informs sources that a packet has exceeded its allocated time to exist

within the network (ICMP Time Exceeded)

4-10 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

Routing with Classical IP over ATM

LANPlex Extended Switching software supports classical IP routing over ATM ARP in an ATM network. Classical IP over ATM uses Logical IP Subnets (LISs) to forward packets within the network environment.

See the LANplex® 2500 Operation Guide for detailed information about the ATM protocol architecture. S ee the LANplex® 2500 Administration Console User Guide for information about how to conﬁgure ATM ports.

About Logical IP

Subnets (LISs)

An LIS is a group of IP nodes that belong to the same subnet, and which are directly connected to a single ATM network. When you add a node to a LIS through the Administration Console IP interface menu, you deﬁne its IP address, subnet mask, and the address an ATM ARP server that supports it.

ATM ARP Servers An ATM ARP server maintains a table of IP addresses and their

corresponding ATM addresses and circuit information. To forward IP packets over an ATM interface, the network node learns the ATM address for the corresponding IP address from the ATM ARP server.

Each ATM ARP server supports a single LIS. You can associated two or more LISs with the same ATM network, but each LIS operates independently of other LISs on the network.

Several types of network nodes can function as ATM ARP servers:

■ Any LANplex system with revision 8.1.0 or later of Extended Switching

software

■ An ATM switch

■ A UNIX® workstation

The following sequence describes how the ATM ARP server learns and stores information about the IP and ATM addresses of nodes in the network.

■ A node establishes a connection to the ATM ARP server

■ The ATM ARP server sends an inverse ATM ARP request to the node,

requesting its IP and ATM address

■ When the node returns this information, the ATM ARP server stores, or

caches, it in the ATM ARP server table.

IP Routing References 4-11

Forwarding to Nodes within an LIS

Nodes can forward packets directly to other nodes in the same LIS. To forward a packet within the same LIS, the sending node requests a translation from the destination IP address to the corresponding ATM address from the ATM ARP server.

■ If the address is known to the server, the server returns a message with this

address

■ If the address is not known to the server, the server returns a message to

advise the sending node that the packet is discarded. When the server returns a destination address, the sending node uses this

learned address to create a virtual circuit ( VC) and to forward this and all subsequent packets to the destination address. The sending node adds this VC to its ATM ARP cache.

IP Routing References

Comer, Douglas E. Internetworking with TCP/IP. Volume I: Principles, Protocols, and Architecture. Englewood Cliffs, New Jersey: Prentice Hall, Inc., 1991.

Perlman, Radia. Interconnections: Bridges and Routers. Reading, Massachusetts: Addison-Wesley Publishing Company, Inc., 1992.

Sterns, Richard. TCP/IP Illustrated. Volume 1: The Protocols. Reading, Massachusetts: Addison-Wesley Professional Computing Services, 1992.

RFC 791. Internet Protocol Speciﬁcation. RFC 792. Internet Control Message Protocol Speciﬁcation. RFC 1009. Requirements for Internet Gateways. RFC 1042. A Standard for the Transmission of IP Datagrams over IEEE 802

Networks. RFC 1058. Routing Information Protocol. RFC 1122. Requirements for Internet Hosts. RFC 1577. Classical IP over ATM.

4-12 CHAPTER 4: ROUTING WITH IP TECHNOLOGY

ROUTING WITH IP MULTICAST

This chapter describes the IP multicast routing implementation on the LANplex® system.

About IP Multicast Routing

IP multicast routing is an extension of the Internet Protocol. Multicast routing allows a router or switch to send packets to a speciﬁc group of hosts without using broadcasts or multiple unicast transmissions. This group can include members that reside on the local LAN, members that reside on different sites within a private network, or members that are scattered throughout the Internet. Mulitcast routing achieves this functionality without loops or excess transmissions.

IP Multicast support within the LANplex system has two main components:

■ Internet Group Management Protocol (IGMP)

■ Distance Vector Multicast Routing Protocol (DVMRP)

This chapter describes these two protocols as well as the algorithms that the LANplex system uses for multicast routing.

IGMP The LANplex system is capable of dynamic multicast ﬁltering based on the

Internet Group Management Protocol (IGMP). This protocol ensures that multicast packets are ﬂooded only to the appropriate ports within a routing interface.

IGMP tracks end-station group membership within a multicast group. Membership in a group is dynamic, and hosts are allowed to be a member of more than one group at a time. Broadcast domains are maintained by avoiding propagation of multicast broadcasts to the entire subnet by conﬁning them within the group (IGMP “snooping”).

5-2 CHAPTER 5: ROUTING WITH IP MULTICAST

DVMRP The Distance Vector Multicast Routing Protocol (DVMRP) establishes

the multicast delivery path over a series of routing devices. DVMRP is a simple distance vector routing protocol, similar to the IP Routing Information Protocol (RIP). Multicast routers exchange distance vector updates that contain lists of destinations as well as the distance in hops to each destination. They maintain this information in a routing table.

DVMRP is the current routing protocol used on the Internet Multicast Backbone (MBONE). Full support of DVMRP allows the LANplex system to fully establish the delivery path without requiring a direct connection to a multicast router.

The MBONE The MBONE is an experimental “Multicast Backbone” network that exists

on the Internet. Users can test multicast applications and technology on the MBONE without waiting for Internet multicast standards to be set. You can gain access to the MBONE through any Internet service provider.

The MBONE routers forward mulitcast packets over an interface or over a multicast tunnel only if the Time-To-Live (T TL) value present in the packet is larger than the tunnel’s threshold. (See the section “Multicast Tunnels” on page 6 for more information about tunnels.)

LANplex 2500 systems at revisions earlier than 8.0 support up to 16 IP multicast tunnels or routing interfaces when connected to the MBONE network. LANplex 2500 systems at revision 8.0 or later can support up to 32 IP multicast tunnels or routing interfaces when connected to the MBONE.

Multicast Routing Algorithms 5-3

Multicast Routing Algorithms

The LANplex system uses three algorithms that support multicast routing:

■ Flooding

■ Spanning Trees

■ Reverse Path Forwarding

Flooding Several types of ﬂooding algorithms exist, but they all share the same

general principles: a node in the network receives a packet that was sent to a multicast destination. The node determines whether the packet is an original that it has not seen before or a duplicate of a packet that it has seen before. If the packet is an original, the node forwards the packet on all interfaces except the incoming inter face. If the packet is a duplicate, the node discards it.

The ﬂooding algorithm is useful in situations where the most important requirement for the network is robustness. I t does not depend on any kind of routing tables. Destinations will receive packets as long as at least one path to them exists and no errors occur during transmission.

Spanning Trees The Spanning Tree algorithm detects loops and logically blocks

redundant paths in the network. The paths form a loopless graph, or tree, spanning all the nodes in the network. A port in the blocking state does not forward or receive data packets.

After the algorithm eliminates extra paths, the network conﬁguration stabilizes. When one or more of the paths in the stable topology fail, the protocol automatically recognizes the changed conﬁguration and activates redundant links. This strategy ensures that all nodes remain connected.

5-4 CHAPTER 5: ROUTING WITH IP MULTICAST

Figure 5-1 shows a simple network with ﬁve links.

Figure 5-1 Simple Network Implemented Without Using Spanning Tree

A spanning tree for this network consists of links 1, 2, 3, and 4. See Figure 5-2.

Figure 5-2 Spanning Tree Algorithm Implemented to Block Redundant Paths

Reverse Path

Forwarding

Reverse path forwarding (RPF) is the multicast algorithm in use on the MBONE network. RPF is designed to avoid duplicate paths on multi-access links. It uses a routing table to compute a logical spanning tree for each network source. The RPF algorithm has these basic steps:

1 When the system receives a multicast packet, the algorithm notes the

source network of the packet and the interface on the LANplex system that received the packet.

2 If the interface belongs to the shortest path towards the source

network, then the system forwards the packet to all interfaces except the interface on which the packet was received.

3 If the condition in Step 2 is false, the system drops the packet.

Multicast Interfaces 5-5

Pruning Pruning is a method used in the RPF algorithm to forward packets to a

spanning tree only if group members exist in the tree. This method results in fewer spanning trees, but it requires dynamic updates to the routing table.

Nodes that are at the border of the network and have no point beyond them in the RPF spanning tree are called leaf nodes. Leaf nodes all receive the ﬁrst multicast packet. If a group member is attached to the leaf node, the node continues to accept packets. If no group member is attached to the leaf node, the node sends back a “prune message” to the router that sent the packet. The message tells the router to send no further packets to this group. In the LANplex system, the Administration Console IP multicast CacheDisplay includes information about when pruning will occur on the spanning tree.

Multicast Interfaces

DVMRP Metric Value The DVMRP metric value determines the cost of a multicast interface. The

Time-To-Live (TTL)

Threshold

Multicast interfaces on the LANplex system have several characteristics which are described in this section:

higher the cost, the slower the link. The default value is 1.

This TTL threshold determines whether the interface will forward multicast packets to other switches and routers in the subnet. If the interface TTL is greater than the packet TTL, then the interface does not forward the packet. The default value is one 1, which means that the interface forwards most packets.

5-6 CHAPTER 5: ROUTING WITH IP MULTICAST

Rate Limit The rate limit determines how many multicast packets can travel over the

interface in kilobytes-per-second. The LANplex system drops multicast trafﬁc that travels faster than this rate. The default is set to 0, which implies no rate limit is set. In all other instances, the lower the rate limit, the more limited the trafﬁc over the interface.

Multicast Tunnels Multicast tunnels are logical connections between two multicast routers

through one or more unicast routers. The multicast router at the local endpoint of the tunnel encapsulates multicast packets in a format that unicast routers can interpret and forward. The multicast router at the remote endpoint decapsulates the packets into their multicast format. Tunnels are virtual links through the unicast IP network.

Multicast tunnels have characteristics similar to those of a multicast interface: a DVMRP metric value, a TTL threshold, and a rate limit. When you deﬁne a multicast tunnel, you also specify the destination address of the remote multicast router that is the remote endpoint of the tunnel.

ROUTING WITH IPX

This chapter provides an overview of IPX routing, including:

■ What part IPX plays in the NetWare environment

■ How IPX works

■ What elements are necessary for IPX routers to transmit packets effectively

IPX Routing in the NetWare

Environment

The NetWare® network operating system was developed and introduced to the market by Novell, Inc. in the early 1980s. Much of the NetWare networking technology was derived from Xerox Network System (XNS) networking system developed by Xerox Corporation.

The NetWare operating system is based on a client/server architecture where clients request certain services from ser vers such as ﬁle access and printer access. As a network operating system environment, the NetWare operating system speciﬁes the upper ﬁve layers of the OSI reference model. It provides ﬁle and printer sharing and supports various applications such as electronic mail and database access.

Figure 6-1 illustrates a simpliﬁed view of NetWare’s better-known protocols and their relationship to the OSI reference model.

, a

6-2 CHAPTER 6: ROUTING WITH IPX

Layers in the OSI reference model

Application

Presentation

Session

Transport

Network

Data Link

Physical

NetBIOS™

Appplications

NetWare®

Shell

(Client)

SPX

NetWare

NetWare®

Control

Protocol

(NCP)

IPX

Media Access Protocols

(Ethernet, FDDI)

Service

Advertising

Protocol

(SAP)

Figure 6-1 NetWare Protocols and the OSI Reference Model

The LANplex system uses the following protocols for routing in a Netware environment:

■ Internet Packet Exchange (IPX)

Routing

Information

Protocol

(RIP)

Internet Packet

Exchange (IPX)

■ Routing Information Protocol (RIP)

■ Service Advertisement Protocol (SAP)

IPX is the primary protocol used for routing in a netware environment. This datagram, connectionless protocol does not require an acknowledgment for each packet sent. Any packet acknowledgment, or connection control, must be provided by protocols above IPX.

IPX deﬁnes internetwork and intranode addressing schemes. IPX internetwork addressing is based on network numbers that are assigned to each interface in an IPX network. IPX intranode addressing is in the form of socket numbers. Since several processes are normally operating within a node, socket numbers provide a type of mail slot so that each process can distinguish itself to IPX.

IPX Routing in the NetWare® Environment 6-3

Routing

Information

Protocol (RIP)

Service Advertising

Protocol (SAP)

RIP allows the exchange of routing information on a NetWare network. IPX routers use RIP to dynamically create and maintain their routing tables.

RIP allows one router to exchange routing information with a neighboring router. As a router becomes aware of any changes in the network layout, it broadcasts this information to any neighboring routers. IPX routers also send periodic RIP broadcast packets containing all routing information known to the router. These broadcasts synchronize all routers on the network and age those networks that might become inaccessible if a router becomes disconnected from the network abnormally.

SAP provides routers and servers that contain SAP agents with a means of exchanging network service information.

Through SAP, servers advertise their ser vices and addresses. Routers gather this information and share it with other routers. This strategy allows routers to dynamically create and maintain a database (server table) of network service information. Clients on the network can determine what services are available and obtain the network address of the nodes (servers) where they can access those services. Clients require this information to initiate a session with a ﬁle server.

SAP allows one router to exchange information with a neighboring SAP agent. As a router’s SAP agent becomes aware of any change in the network server layout, it immediately broadcasts this information to any neighboring SAP agents. The router also periodically sends SAP broadcast packets containing all server information known to the SAP agent. These broadcasts synchronize all servers on the network and age those servers that might become inaccessible because of any abnormal shut down of the router or server.

6-4 CHAPTER 6: ROUTING WITH IPX

How IPX Routing Works

A router operates at the network layer of the OSI Reference Model. This means that it receives its instructions to route packets from one segment to another from a network-layer protocol. IPX, with the help of RIP, performs these network layer tasks. These tasks include addressing, routing, and switching information packets to move single packets from one location to another. This section ﬁrst describes the information included in an IPX packet that helps it get delivered and then it describes the IPX packet delivery process.

IPX Packet Format The IPX packet format consists of two parts: a 30-byte header and a data

portion. The network, node, and socket address for both the destination and source are held within the packet’s IPX header.

Figure 6-2 shows the IPX packet format.

Checksum Packet Length Transport Control

(1 byte) Destination Network

(2 bytes) (2 bytes) Packet Type

(1 byte)

(4 bytes) Destination Node Destination Socket Source Network

Source Node Source Socket

Upper-layer Data

(6 bytes)

(2 bytes)

(4 bytes)

(6 bytes)

(2 bytes)

Figure 6-2 IPX Packet Format

How IPX Routing Works 6-5

The packet format consists of the following elements:

■ Checksum — The IPX packet begins with a 16-bit checksum ﬁeld that is set

to 1s.

■ Packet Length — This 16-bit ﬁeld contains the length, in bytes, of the

complete network packet. This ﬁeld includes both the IPX header and the data. The IPX length must be at least 30 bytes.

■ Transport Control — This 1-byte ﬁeld indicates how many routers a packet

has passed through on its way to its destination. Packets are discarded when this value reaches 16. A sending node always sets this ﬁeld to 0 when building an IPX packet.

■ Packet Type — This 1-byte ﬁeld speciﬁes the upper-layer protocol that will

receive the packet’s information.

■ Destination Network — This 4-byte ﬁeld provides the destination node’s

network number. When a sending node sets this ﬁeld to zero, the destination node is assumed to be on the same local segment as the sending node.

■ Destination Node — This 6-byte ﬁeld contains the physical address of the

destination node.

■ Destination Socket — This 2-byte ﬁeld contains the socket address of the

packet’s destination process.

■ Source Network — This 4-byte ﬁeld provides the source node’s network

number. If a sending node sets this ﬁeld to 0, it means the source’s local network is unknown.

■ Source Node — This 6-byte ﬁeld contains the physical address of the

source node. Broadcast addresses are not allowed.

■ Source Socket — This 2-byte ﬁeld contains the socket address of the

process that transmitted the packet.

■ Upper-layer Data — The data ﬁeld contains information for the upper-layer

processes.

6-6 CHAPTER 6: ROUTING WITH IPX

IPX Packet Delivery On a NetWare network, the successful delivery of a packet depends both on

the proper addressing of the packet and on the internetwork conﬁguration. Packet addressing is handled in the packet’s Media Access Control (MAC) protocol header and IPX header address ﬁelds.

To send a packet to another node, the sending node must know the complete internetwork address including the network, node, and socket of the destination node. Once the sending node has the destination node’s address, it can proceed with addressing the packet. However, the way the MAC header of that packet is addressed depends on whether the sending and destination nodes are separated by a router. See Figure 6-3.

Sending Node Router Destination Node

Network = 000000AA Node = 000000000001 Socket = 4003

Node Node 000000000020 000000000021

Network = 000000BB Node = 000000000003 Socket = 0451

MAC Header

Destination Node = 000000000020 Source Node = 000000000001

IPX Header

Checksum = FFFF Packet Length = 011E Tranport Control = 00 Packet Type = 11

Dest Network = 000000BB Dest Node = 000000000003 Dest Socket = 0451

Source Network = 000000AA Source Node = 000000000001 Source Socket = 4003

Data

MAC Header

Destination Node = 000000000003 Source Node = 000000000021

IPX Header

Checksum = FFFF Packet Length = 011E Tranport Control = 01 Packet Type = 11

Dest Network = 000000BB Dest Node = 000000000003 Dest Socket = 0451

Source Network = 000000AA Source Node = 000000000001 Source Socket = 4003

Data

Figure 6-3 IPX Packet Routing

Sending Node’s Responsibility

When a node needs to send information to another node with the same network number, the sending node can simply address and send packets directly to the destination node. However, if the sending and receiving nodes have different network numbers, the sending node must ﬁnd a router on its own network segment that can forward packets to the destination node’s network segment.

How IPX Routing Works 6-7

To ﬁnd this router, the sending node broadcasts a RIP packet requesting the best route to the destination node’s network number. The router residing on the sending node’s segment with the shortest path to the destination segment responds to the RIP request. The router’s response includes its network and node address in the IPX header. If the sending node is a router rather than a workstation, the router can get this information from its internal routing tables and need not send a RIP request.

Once the sending node knows the router’s node address, it can send packets to the destination node.

Router’s Responsibility

When a router receives an IPX packet, it handles the packet in one of two ways:

■ If the packet is destined for a network number to which the router is

directly connected, the router performs the following tasks:

■ Places the destination node address from the IPX header in the

destination address ﬁeld of the MAC header.

■ Places its own node address in the source address ﬁeld of the MAC

header.

■ Increments the Transport Control ﬁeld of the IPX header and transmits

the packet on the destination node segment.

■ If the packet is destined for a network number to which the router is not

directly connected, the router sends the packet to the next router along the path to the destination node as follows:

■ The router looks up the node address (in the routing information table)

of the next router and places the address in the destination address ﬁeld of the packet’s MAC header. For more information on routing tables, see the next section.

■ The router places its own node address in the source address ﬁeld of the

packet’s MAC header.

■ The router increments the Transport Control ﬁeld in the IPX header and

sends the packet to the next router.

6-8 CHAPTER 6: ROUTING WITH IPX

The Elements of IPX Routing

IPX routers use the following elements to transmit packets over an intranetwork:

■ Router interfaces

■ Routing tables

■ Service Advertising Protocol (SAP)

Router Interfaces A router inter face is the connection between the router and the network

number (address). In traditional routing models, the inter face would be the same as the port, because only one interface can exist per port.

In the LANplex system’s IPX routing, more than one por t can be connected to the network number. Therefore, the router interface is the relationship between the ports and the network number (address) in your IPX network.

Each router interface has a network address. This address deﬁnes the network number to which the router interface is attached. The router interface’s IPX address serves two functions:

■ It is used when sending IPX packets to or from the router itself.

■ It deﬁnes the network number of the segment connected to that inter face.

Routing Tables A routing table holds information about all the network segments. It allows

a router to send a packet toward its ultimate destination using the best possible route. The routing information table contains an entry for every network number that the router currently knows exists. A router uses the routing information table when the destination network number of the packet it is sending is not on a network to which it is directly connected. The routing information table provides the immediate address of a forwarding router that can forward the packet toward its destination.

The routing table consists of the following elements:

■ Interface — Identiﬁes the number of the router’s interface that will be used

to reach the speciﬁc network segment.

■ Address — Identiﬁes the addresses for segments that the router currently

knows exists.

The Elements of IPX Routing 6-9

■ Hops to Network — Provides the number of routers that must be crossed

to reach the network segment.

■ Ticks to Network — Provides an estimate of the time necessary to reach

the destination segment.

■ Node — The node address of the router that can forward packets to each

segment. When set to all zeroes, the route is directly connected.

■ Aging Timer — The time since the network’s last update.

Figure 6-4 shows an example of a typical routing information table.

Routing Table Interface Address Hops Ticks Node Age

1 1 1 1 00-00-00-00-00-00 0 2 45469f30 1 1 00-00-00-00-00-00 0 2 45469f33 2 3 08-00-17-04-33-45 40

Figure 6-4 Routing Table Example

Generating Routing Table Information

The routing information table is generated and updated as follows:

■ Statically — You manually enter routes. They do not change until you

change them (they do not time out).

■ Dynamically — The router uses RIP to exchange information with other

routers. Routes are recalculated at regular intervals. Static Routes. A static route is one you manually conﬁgure in the routing

table. Static routes are useful in environments where no routing protocol is used or where you want to override some of the routes generated with a routing protocol. Because static routes do not automatically change in response to network topology changes, you should manually conﬁgure only a small number of reasonably stable routes.

Dynamic Routes Using RIP. Automated methods of learning routes help you keep up with a changing network environment, allowing routes to be reconﬁgured quickly and reliably. Interior Gateway Protocols (IGP), which operate within intranetworks, provide this automated method. The LANplex

6-10 CHAPTER 6: ROUTING WITH IPX

system uses RIP (one of the most widely used IGPs), to dynamically build its routing tables.

RIP operates in terms of active and passive devices. The active devices, usually routers, broadcast their RIP messages to all devices in a network; they update their own routing tables when they receive a RIP message. The passive devices, usually hosts, listen for RIP messages and update their routing tables; they do not send RIP messages.

An active router sends a RIP message every 60 seconds. This message contains both the network number for each destination network and the number of hops to reach it. In RIP, each router that a packet must travel through to reach a destination equals one hop.

Selecting the Best Route

Large networks have multiple routes to a single network. The routers use these criteria to select the best “route” to a network when choosing between alternate routes:

Service Advertising

Protocol

■ Select the route that requires the lowest number of ticks.

■ If multiple routes exist with an equal number of ticks, select the route that

also has the lowest number of hops.

■ If multiple routes exist with both ticks and hops equal, choose any of the

routes as the “best ” route.

The Service Advertising Protocol (SAP) allows servers (for example, ﬁle servers, print servers, and gateway servers) to advertise their addresses and services. Through the use of SAP, adding and removing services on an internetwork becomes dynamic. As servers are booted up, they advertise their services using SAP. When they are brought down, they use SAP to indicate that their services are no longer available.

Internetwork Service Information

Using SAP, routers create and maintain a database of internetwork service information. Clients on use this data to determine what services are available on the network and to obtain the internetwork address of the nodes (servers) where they can access desired services.

The Elements of IPX Routing 6-11

A workstation must ﬁrst know a server’s network address before it can initiate a session with a ﬁle server.

SAP Packet Structure

SAP uses IPX and the medium-access protocols for its transport. The packet structure allows the following functions:

■ A workstation request for the name and address of the nearest server of a

certain type

■ A router request for the names and addresses of all the servers or of all the

servers of a certain type on the internet work

■ A response to a workstation or a router request

■ Periodic broadcasts by servers and routers

■ Changed server information broadcasts

Figure 6-5 provides an overview of the SAP packet structure. Note that the packet structure is encapsulated within the data area of IPX.

IPX Packet Format

IPX Header (30 bytes)

Packet Type = 4 Socket = 452h

Data

SAP Packet Structure

Operation (2 bytes)

Server Entry (1) (64 bytes)

. . .

Server Entry (n) (64 bytes) (n <= 7)

Figure 6-5 SAP Packet Structure

Server Entry Structure

Service Type (2 bytes) Server Name (48 bytes)

Network Address (4 bytes) Node Address (6 bytes) Socket Address (2 bytes) Hops to Server (2 bytes)

6-12 CHAPTER 6: ROUTING WITH IPX

A SAP packet consists of the following ﬁelds:

■ Operation — This ﬁeld indicates the type of operation the SAP packet

performs. It can be set to one of the following values:

1=Request 2=Response 3=Get Nearest Server Request 4=Get Nearest Server Response

■ Server Entry — Each 64-byte ser ver entry includes information about a

particular server. It consists of the following ﬁelds:

■ Service Type — This 2-byte ﬁeld identiﬁes the type of service the ser ver

provides.

Although IPX routers use SAP, routers typically do not act as servers and require no Service Type assignment.

■ Server Name — This ﬁeld contains the 48-byte character string name

that is assigned to a server. The server name, in combination with the service type, uniquely identiﬁes a server on an internetwork.

■ Network Address — This 4-byte ﬁeld contains the server’s network

address.

■ Node Address — This 6-byte ﬁeld contains the server’s node address.

■ Socket Address — This 2-byte ﬁeld contains the socket number that

the server uses to receive service requests.

■ Hops to Server — This 2-byte ﬁeld indicates the number of

intermediate networks that must be passed through to reach the server associated with this ﬁeld entry. Each time the packet passes through an intermediate network, the ﬁeld is incremented by 1.

By using SAP, servers can advertise their services and addresses. The information that these servers broadcast is not directly used by clients; rather it is collected by a SAP agent within each router on the server’s segment. The SAP agents store this information in a server information table. If the agents reside within a server, the information is also stored in their server’s bindery. The clients can then contact the nearest router or ﬁle server SAP agent for server information.

The Elements of IPX Routing 6-13

The SAP broadcasts that servers and routers send are local and, therefore, only received by SAP agents on their connected segments. However, SAP agents periodically broadcast their server information so that all SAP agents on the internetwork have information about all servers that are active on the internetwork.

Server Information Table

A server information table holds information about all the servers on the internetwork. SAP agents use this table to store information received in SAP broadcasts. Figure 6-6 shows an example of a typical server information table.

Server Table

Interface Name Type Network Node Socket Hops Age

1 LPX1102 4 45469f33 00-00-00-00-00-01 451 2 102 1 LPX1103 4 45469f44 00-00-00-00-00-01 451 5 65 2 LPX2001 4 45470001 00-00-00-00-00-01 451 4 33

Figure 6-6 Server Information Table

The server information table provides the following information:

■ Interface — Indicates from which interface the information was received

■ Server Name — The name of the server

■ Server Type — Indicates the type of ser vice provided

■ Network Address — The address of the network on which the server

resides

■ Node Address — The node of the server

■ Socket Address — The socket number on which the server will receive

service requests

■ Hops to Server — The number of intermediate networks that must be

passed through to reach the server associated with this entry

■ Age of Server — The time since the last update for that server

The server information table is either statically or dynamically generated and updated.

6-14 CHAPTER 6: ROUTING WITH IPX

Static Servers. A static server is one you manually conﬁgure in the server information table. Static servers are useful in environments where no routing protocol is used or where you want to override some of the servers generated with a routing/server protocol. Because static servers do not automatically change in response to network topology changes, you should manually conﬁgure only a small number of relatively stable servers.

Dynamic Routes Using SAP. An automated method of adding and removing services helps you keep up with a changing network environment, allowing servers to advertise their services and addresses quickly and reliably. SAP provides this automated method.

As servers are booted up, they advertise their services using SAP. When servers are brought down, they use SAP to indicate that their services are no longer available.

The information that these servers broadcast is not directly used by clients; rather it is collected by a SAP agent within each router on the server’s segment. The SAP agents store this information in the server information table. Clients can then use the table to contact the nearest router or ﬁle server SAP agent for server information.

Server Information Maintenance

When a router’s SAP agent receives a SAP broadcast response indicating a change in the internetwork server conﬁguration, the agent must update its server information table and inform other SAP agents of these changes. Examples of such a change are when a server is disconnected or becomes accessible through a better route.

To relay this changed information to the rest of the internetwork, the SAP agent immediately sends a broadcast to all of its directly connected segments except the segment from which the information was received. This broadcast packet contains information regarding the server change. The change information is also reﬂected in all future periodic broadcasts.

SAP Aging. Router SAP agents implement an aging mechanism to handle conditions that cause a SAP agent to go down suddenly without sending a DOWN broadcast. Examples of such changes are a hardware failure, power interruptions, and power surges. A SAP agent maintains a timer for each entry in its server information tables that keeps track of how much time has

The Elements of IPX Routing 6-15

elapsed since information was received concerning a particular table entry. Since this information is either new or changed, the SAP agent that receives this information immediately passes it on, and the change is quickly learned throughout the internetwork.

SAP Request Handling. When a SAP agent receives a general request, it sends the sending source a SAP response packet containing information about all servers of any type known to the receiving SAP agent. This response includes the same information sent out in a periodic broadcast. When the request is speciﬁc, the SAP agent sends a SAP response directly to the requesting node. This response contains all known information regarding all servers of the requested type.

6-16 CHAPTER 6: ROUTING WITH IPX

ROUTING IN AN APPLETALK®

NVIRONMENT

This chapter provides an overview of AppleTalk® routing, and includes these topics:

■ AppleTalk Network Elements

■ AppleTalk Protocols

■ About AARP

About AppleTalk® AppleTalk is a suite of protocols deﬁned by Apple Computer, Inc., for

connecting computers, peripherals devices, and other equipment on a network. AppleTalk protocols support most of the functions offered by the Open Standards Interconnect (OSI) reference model.

The AppleTalk protocols work together to provide ﬁle sharing and printer sharing, as well as applications like electronic mail and database access. All Macintosh® computers have AppleTalk connectivity options built into them, making it the de facto standard for Apple® computer networks.

AppleTalk® Network Elements

An AppleTalk network consists of different nodes in groups of networks in an AppleTalk internet. These nodes can include workstations, routers, and printers, or services for other computers, called clients.

This section describes the elements of an AppleTalk internet:

■ AppleTalk networks

■ AppleTalk nodes

■ AppleTalk zones

■ Seed routers

7-2 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

AppleTalk®

Networks

A network in an AppleTalk internet is a cable segment attached to a router. Each network is identiﬁed by a network number or range of network numbers. The network administrator assigns these numbers from a range of valid network numbers.

Two AppleTalk network numbering systems are currently in use: nonextended (Phase 1) and extended (Phase 2). 3Com routers support extended network numbers. While the LANplex system will not translate Phase 1 packets to Phase 2 packets, it will route packets to a Phase 1 network. The LANplex system anticipates that a gateway exists between the two networks to translate the packets.

An extended network can span a range of logical networks. Network numbers in an extended network consist of a range, such as 15 through 20. This numbering scheme allows for as many as 16,580,608 nodes, although the actual cables will not support this many nodes.

AppleTalk® Nodes A node in a AppleTalk network is any addressable device, including

workstations, printers, and routers. Nodes are physically attached to a network. Each AppleTalk node is identiﬁed by a unique AppleTalk address that each node selects at initialization. The address consists of the node’s network number and a unique node number.

Named Entities

When a device on the network provides a service for other users, the network administrator can give the device a name. The name appears on the Chooser menu of the Macintosh with an associated icon. For example, the Chooser of the Macintosh can include a printer icon. When you select the printer icon, several printer names can appear in a list, such as Laser1, or Laser 2. The Name Binding Protocol (NBP), described later in this chapter, translates these device names into AppleTalk addresses.

AppleTalk® Network Elements 7-3

AppleTalk® Zones An AppleTalk zone is a logical collection of nodes on an AppleTalk internet.

A zone can include all nodes in a single network or a collection of nodes in different networks. You assign a unique name to each zone to identify it in the internet. Figure 7-1 illustrates the relationship between physical AppleTalk networks and logical AppleTalk zones.

Network 8-8

Network 20-40

Router

Network 47-47

Zone: Administration

Zone: Accounting

Router

Zone: Marketing

Figure 7-1 AppleTalk Networks and AppleTalk Zones

Figure 7-1 shows an AppleTalk internet with three networks: 47-47, 20-40, and 8-8. Three AppleTalk zones span the networks in this internet: Administration, Accounting, and Mark eting. Network 20-40 includes two nodes in the Administration zone and ﬁve nodes in the Accounting zone. Network 47-47 includes a node from the Accounting zone as well as the Marketing nodes. Network 8-8 consists of nodes in the Administration zone only.

Creating zones within a network reduces the amount of searching a router has to do to ﬁnd a resource on the network. For example, you may want to gain access to a printer on the network. Instead of searching the whole network when you want to print a ﬁle to a certain printer, the router searches for it within a particular zone. You gain access to the printer more

7-4 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

quickly within the zone because the zone includes fewer devices than the entire internet does.

Seed Routers A seed router initializes the internet with AppleTalk conﬁguration

information, including network numbers and zone names. The seed router broadcasts this information so that nonseed routers can learn it. You can designate a seed router through the Administration Console.

A nonseed router listens for a seed router and then takes the conﬁguration information from the ﬁrst seed router it detects. After a nonseed router obtains the conﬁguration information, it can participate in the network as if it were a seed router as well.

AppleTalk Protocols

AppleTalk protocols work together to ensure the seamless ﬂow of information throughout the AppleTalk internet. Figure 7-2 shows a simpliﬁed view of AppleTalk protocols and their relationship to the OSI reference model. Together, these protocols provide the following services:

■ Physical Connectivity

■ End-to-End Services

■ Reliable Data Delivery

OSI Reference Model

AppleTalk Protocols 7-5

Application

Presentation

Session

Transport

Network

Link

Physical

AppleTalk

Data Stream

Protocol (ADSP)

Routing T able

Maintenance

Protocol (RTMP)

Zone Information

TokenTalk Link Access

Protocol

Token Ring

Hardware

AppleTalk

Filing

Protocol (AFP)

AppleTalk

Protocol (ZIP)

AppleTalk Echo Protocol (AEP)

Datagram Delivery Protocol (DDP)

EtherTalk

Link Access

Protocol

Ethernet

Hardware

Session

Protocol (ASP)

AppleTalk

Transaction

Protocol (ATP)

LocalTalk

Link Access

Protocol

LocalTalk

Hardware

PostScript

Printer Access

Protocoo (PAP)

Name Binding

Protocol (NBP)

Figure 7-2 AppleTalk Protocols and the OSI Reference Model

The AppleTalk six-layer protocol suite is not fully compliant with the OSI seven-layer reference model. However, AppleTalk provides many of the functions and services provided by OSI. Note that AppleTalk has no speciﬁc protocols for the application layer, since the lower levels provide printer and ﬁle service.

Physical

Connectivity

The physical layer of the OSI protocol stack deﬁnes the network hardware. You can use standard network hardware, such as that deﬁned for Ethernet and Token Ring networks, with AppleTalk. Apple has also deﬁned its own network hardware, called LocalTalk, which uses a synchronous RS-422A bus for communications.

The data link layer provides the interface between the network hardware and the upper layers of the protocol stack. The AppleTalk data link layer includes three link access protocols (LAPs): TokenTalk LAP (TLAP), Ethernet LAP (ELAP), and LocalTalk Link Access Protocol (LLAP).

The AppleTalk Address Resolution Protocol (AARP), which translates hardware addresses to AppleTalk addresses, also exists at the datalink layer

7-6 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

because it is closely related to the Ethernet and token ring LAPs. This protocol is usually included in the deﬁnition of each LAP, so it does not appear in the reference model. See the section “About AARP” later in this chapter for more information about this protocol.

The Datagram

Delivery Protocol

(DDP)

The network layer accepts data from the layers above it and divides the data into packets that can be sent over the network through the layers below it. The Datagram Delivery Protocol (DDP) transfers data in packets called datagrams.

Datagram delivery is the basis for building other AppleTalk services, such as electronic mail. The DDP allows AppleTalk to run as a process-to-process, best-effort delivery system in which the processes running in the nodes of interconnected networks can exchange packets with each other.

End-to-End Services The transport layer and the session layer provide end-to-end services in the

AppleTalk network. These services ensure that routers transmit data accurately between one another. Each layer includes four protocols that work together to support these services. This section describes these protocols and provides more detail for those that you can view using the LANplex Administration Console.

Transport Layer Protocols

An AppleTalk internet has four transport layer protocols:

■ Routing Table M aintenance Protocol (RTMP)

■ AppleTalk Echo Protocol (AEP)

■ AppleTalk Transaction Protocol (ATP)

■ Name Binding Protocol (NBP)

Routing Table Maintenance Protocol (RTMP). The protocol maintains information about AppleTalk addresses and connections between different networks. It speciﬁes that each router 1) learns about new routes from the other routers and 2) deletes routes after a certain period if the local router no longer broadcasts the route to the network.

AppleTalk Protocols 7-7

Each router builds a routing table that is the basis of dynamic routing operations in an AppleTalk internet. Every 10 seconds, each router sends an RTMP data packet to the network. Routers use the information that they receive in the RTMP broadcasts to build their routing tables. Each entr y in the routing table contains these items:

■ The network range

■ The distance in hops to the destination network

■ The interface number of the destination network

■ The state of each port (good, suspect, bad, really bad)

The router uses these items to determine the best path along which to forward a data packet to its destination on the network. The routing table contains an entry for each network that a datagram can reach within 15 hops of the router. The table is aged at set intervals as follows:

1 After a period of time, the RTMP changes the status of an entr y from good

to suspect.

2 After an additional period of time, the RTMP changes the status of an entr y

from suspect to bad.

3 After an additional period of time, the RTMP changes the status of an entr y

from bad to really bad.

4 Finally, the router removes from the table the entry of a nonresponding

router with a really bad status. The data in the routing table is cross-referenced to the Zone Information

Table (ZIT). This table maps networks into zones. The section on the session layer protocols includes information about the ZIT.

Figure 7-3 illustrates a simple AppleTalk network and Table 7-1 shows the corresponding routing table.

7-8 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

Network 5-5

Router 802

Router 801

Network 64-64

Router 36

Network 18-20

Interface 2

Router 24

Interface 1

Network 103-103

Interface 3

Router 200

Network 12-12

Figure 7-3 A Simple AppleTalk Network

Table 7-1 The Routing Table for Router 24 in Figure 7-3

Network Range Distance Interface State

5-5 1 2 Good 12-12 3 3 Good 18-20 2 3 Good 103-103 0 1 Good 64-64 1 3 Good

You can view the AppleTalk routing tables in your network through the Administration Console.

AppleTalk Echo Protocol (AEP). AppleTalk nodes use the AEP to send datagrams to other nodes in the network. It causes the destination node to return, or echo, the datagram to the sending node. This protocol can determine whether a node is accessible before any sessions are started, and it can enable users to estimate the round-trip delay time between two nodes.

AppleTalk Protocols 7-9

AppleTalk Transaction Protocol (ATP). This protocol, along with the AppleTalk Data Stream Protocol (ADSP), ensures that DDP packets are delivered to a destination without any losses or corruption.

Name Binding Protocol (NBP). This protocol translates alphanumeric entity names to AppleTalk addresses. It maintains a table that references the addresses of nodes and named entities that reside in that node. Because each node maintains its own list of named entities, the names directory within an AppleTalk network is not centralized. It is a distributed database of all nodes on the internet.

The Session Layer Protocols

An AppleTalk internet has four session-layer protocols:

■ Zone Information Protocol (ZIP)

■ AppleTalk Data Stream Protocol (ADSP)

■ AppleTalk Session Layer Protocol (ASP)

■ Printer Access Protocol (PAP)

The Zone Information Protocol (ZIP). ZIP works with RTMP to maintain a table that maps network numbers to network zones for the entire AppleTalk internet. Network zones are the logical groupings of AppleTalk networks. As we have seen it, the table created by ZIP is called the Zone Information Table (ZIT). The Administration Console allows you to view the zone information table by network number or network zone.

ZIP creates a zone information table in each router. Each entry in the ZIT is a “tuple,” or pair, that includes a network number and a network zone name. When an NBP packet arrives at the router, it includes the zone name which the router compares with entries in the zone table. The router then matches the network number from the matching ZIT tuple to the one in the RTMP table to ﬁnd the interface where it can route the packets.

7-10 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

AppleTalk Data Stream Protocol (ADSP). The ADSP works with the ATP to ensure reliable data transmission. Unlike ATP, however, ADSP provides full-duplex byte-stream delivery. This means that two nodes can communicate simultaneously. ASDP also includes ﬂow control, so that a fast sender does not overwhelm a slow receiver.

AppleTalk Session Protocol (ASP). The ASP passes commands between a workstation and a server once a connection is made between the two. ASP ensures that the commands are delivered in the same order as they were sent and returns the results of these commands to the workstation.

Printer Access Protocol (PAP). The PAP maintains communications between a workstation and a printer or print service. The PAP functions include setting up and maintaining a connection, transferring the data, and tearing down the connection on completion of the job. Like other protocols at the session layer, PAP relies on NBP to ﬁnd the addresses of named entities. PAP also depends on ATP for sending data.

Presentation Layer The presentation layer maintains information about ﬁles, formats, and

translations between formats. An AppleTalk internet has two protocols at the presentation layer: the AppleTalk Filing Protocol (AFP) and PostScript®. AFP provides remote access to ﬁles on the network. PostScript is a paged description language used by many printers.

About AARP The AppleTalk Address Resolution Protocol (AARP) maps the hardware

address of an AppleTalk node to an AppleTalk protocol address. It does this mapping for both extended and nonextended networks.

When a node on the network initializes, it randomly selects an AppleTalk address for itself. At the same time, it sends out ten AARP probe packets. The probe packets determine whether any other nodes on the network are using the address it has chosen. If a node on the network is already using that address, the node randomly selects another address and sends out another probe packet.

About AARP 7-11

The AARP maintains an Address Mapping Table (AMT) with the most recently used hardware addresses and their corresponding AARP addresses. If an address is not in this table, AARP sends a request to the protocol address and adds the hardware address to the table when the destination node replies. You can view this table, called the AARP cache, through the LANplex Administration Console.

7-12 CHAPTER 7: ROUTING IN AN APPLETALK® ENVIRONMENT

ADMINISTERING VLANS

This chapter describes how to display information about VLANs and how to conﬁgure VLANs.

Through the Administration Console, you can:

■ Display summary or detailed information on VLANs

■ Deﬁne or modify a VLAN deﬁnition

■ Delete a VLAN deﬁnition

Displaying VLAN Information

Top-Level Menu

system ethernet fddi

display

atm ip

ipx appletalk snmp analyzer script logout

mode ipFragmentation ipxSnapTranslation addressThreshold agingTime stpState stpPriority stpMaxAge stpHelloTIme stpForwardDelay stpGroupAddress port packetFilter

➧ vlan

➧ summary ➧ detail

define modify remove

➧ bridge

You can display a summary of VLAN information or a detailed report. When you display a summary, you receive information about the protocols and ports assigned to each VLAN plus the layer 3 addresses used to manage ﬂood domains for overlapping IP subnets. The detailed VLAN report includes the summary information plus additional utilization statistics.

From the top level of the Administration Console, enter:

bridge vlan summary

bridge vlan detail

The VLAN information is displayed in the format you speciﬁed. Example of a summary display for several VLANs:

Select menu option (bridge/vlan): summary

Index Protocol Identifier Ports

1 default 0 1-17 2 IP 2 1, 5-7 3 IPX 3 8-10 4 IP 4 7, 12-15

8-2 CHAPTER 8: ADMINISTERING VLANS

Index Name Layer 3

1 none 2 eastgroup 158.101.111.16 255.255.255.0 3 westgroup none 4 northgroup 158.101.112.14 255.255.255.0

Example of a detailed display for the VLANs:

Select menu option (bridge/vlan): detail

Index Protocol Identifier Ports

1 default 0 1-17 2 IP 2 1, 5-7 3 IPX 3 8-10 4 IP 4 7, 12-15

Index Name Layer 3

1 none 2 eastgroup 158.101.111.16 255.255.255.0 3 westgroup none 4 northgroup 158.101.112.14 255.255.255.0

index inPackets inBytes outPackets outBytes

1 342 3676 322 2987 2 125 7654 118 6897 3 345 7554 289 7431 4 876 8651 765 7969

Table 8-1 describes these statistics.

Table 8-1 Fields for VLAN Information

Field

Index A system-assigned index used for identifying a particular VLAN Protocol The protocol suite of the VLAN Identifier A unique, user-defined (4-byte) integer for use by global

Ports The numbers of the ports assigned to the VLAN Name A 16-byte character string intended to identify the members of the

Layer 3 Optional parameters consisting of IP subnet and mask used to set

continued

Description

management operations

VLAN

up flood domains for overlapping IP VLAN subnets

Defining VLAN Information 8-3

Table 8-1 Fields for VLAN Information (continued)

Deﬁning VLAN Information

Top-Level Menu

system ethernet fddi atm

➧ bridge

ip ipx appletalk snmp analyzer script logout

display mode ipFragmentation ipxSnapTranslation addressThreshold agingTime stpState stpPriority stpMaxAge stpHelloTIme stpForwardDelay stpGroupAddress port packetFilter

➧ vlan

summary detail

➧ define

modify remove

Field

Description

inPackets Number of flooded broadcast and multicast packets that were

received on the VLAN

inBytes Number of flooded broadcast and multicast bytes that were

received on the VLAN

outPackets Number of flooded broadcast and multicast packets transmitted

over the VLAN

outBytes Number of flooded broadcast and multicast bytes transmitted over

the VLAN

Follow these steps to create a VLAN deﬁnition:

1 From the top level of the Administration Console, enter :

bridge vlan define

2 Enter the appropriate protocol suite: (IP, IPX, AppleTalk, XNS,

DECnet, SNA, Banyan, X.25, NetBIOS, NetBEUI, default

3 Enter the VLAN interface identiﬁer. 4 Enter the VLAN name, enclosed in quotation marks. 5 Enter the number(s) of the port(s) or

all to assign all ports to the VLAN.

)

You are prompted to enter the number(s) of the port(s) that can be assigned to the VLAN.

If you did not choose the IP protocol suite for this VLAN, you have completed the steps for deﬁning the VLAN.

If you selected the IP protocol suite, follow these steps:

1 Enter

defined to use layer 3 subnet addressing and continue with steps 2

and 3, OR enter

undefined to not use layer 3 addressing.

2 Enter the IP subnet address. 3 Enter the subnet mask.

8-4 CHAPTER 8: ADMINISTERING VLANS

Example:

Select menu option (bridge/vlan): define Enter Protocol Suite (IP,IPX,AppleTalk,XNS,DECnet,SNA,Banyan,X.25,NetBIOS,NeBEUI, default): Enter VLAN Identifier: 1 Enter VLAN Name: “SD Marketing” Ports 1=FDDI, 2-17=Ethernet Enter port(s) (1-17|all): Layer 3 Address (undefined, defined): defined Enter IP Subnet Address: 158.111.122.0 Enter subnet mask [255.255.0.0] 255.255.255.0

The maximum number of VLANs you can deﬁne on a single bridge is 32.

1-5

Modifying VLAN Information

Top-Level Menu

system ethernet fddi

display

atm ip

ipx appletalk snmp analyzer script logout

mode ipFragmentation ipxSnapTranslation addressThreshold agingTime stpState stpPriority stpMaxAge stpHelloTIme stpForwardDelay stpGroupAddress port packetFilter

➧ vlan

summary detail define

➧ modify

remove

➧ bridge

To modify VLAN information:

1 From the top level of the Administration Console, enter :

bridge vlan modify

You are prompted to reenter the information that deﬁnes the VLAN. Press the Return or Enter key to accept any value that appears in brackets [ ].

2 Enter the number of the VLAN interface index. 3 Enter the protocol suite for that VLAN:

DECnet, SNA, Banyan, X.25, NetBIOS, NetBEUI, default)

(IP, IPX, AppleTalk, XNS,

4 Enter the VLAN identiﬁer. 5 Enter the VLAN name. 6 Enter the number(s) of the port(s) or all. 7 If you have selected the IP protocol suite and want to use the Layer 3

address information, enter defined for layer 3 addressing. Enter undefined if you do not want layer 3 addressing.

Removing VLAN Information 8-5

Example:

Select menu option (bridge/vlan): modify Select VLAN interface [1-2]: 2 Protocol Suite (IP,IPX,AppleTalk,XNS,DECnet,SNA, Banyan,X.25,NetBIOS,NetBEUI,default) [AppleTalk]: VLAN Identifier [1]: 2 VLAN Name [Sales]: Ports 1=FDDI, 2-17=Ethernet Enter port(s) (1-17|all) [1-5]: Layer 3 Address (undefined,defined) [undefined]:

Removing VLAN Information

Top-Level Menu

system ethernet fddi atm

➧ bridge

ip ipx appletalk snmp analyzer script logout

display mode ipFragmentation ipxSnapTranslation addressThreshold agingTime stpState stpPriority stpMaxAge stpHelloTIme stpForwardDelay stpGroupAddress port packetFilter

➧ vlan

summary detail define modify

➧ remove

Follow these steps to remove a VLAN deﬁnition:

1 From the top level of the Administration Console, enter :

bridge vlan remove

2 Enter the indexes for the VLANs you want to remove.

Example:

Select menu option (bridge/vlan): remove Select VLAN index(es) (1-2|all): 1

8-6 CHAPTER 8: ADMINISTERING VLANS

ADMINISTERING IP ROUTING

This chapter describes how to set up your LANplex® system to use the Internet Protocol (IP). For more information about how IP works, see Part III of this guide.

You can display or conﬁgure the following IP characteristics on your LANplex system:

■ IP interfaces

■ Routes

■ Address Resolution Protocol (ARP) cache

■ UDP Helper

■ ATM ARP Server (for LANplex systems with ATM modules)

■ IP Routing

Administering interfaces

■ ICMP Router Discovery

■ Routing Information Protocol (RIP)

■ Ping

■ IP statistics

You can deﬁne two types of IP interfaces through LANplex Ex tended Switching software: IP VLAN interfaces and IP LIS interfaces. This section describes these interfaces and how to administer them.

An IP VLAN interface deﬁnes the relationship between an IP Virtual LAN (VLAN) and the subnets in the IP net work. Every IP VLAN interface has one IP VLAN associated with it. Each Ethernet or FDDI switching module has one interface deﬁned for each subnet directly connected to it. You must ﬁrst deﬁne a VLAN, as described in Chapter 8, Administering VLANs, before you deﬁne an associated IP VLAN interface.

9-2 CHAPTER 9: ADMINISTERING IP ROUTING

LIS Interfaces A logical IP subnet (LIS) inter face supports logical IP over ATM. You deﬁne

LIS interfaces for the ports on ATM modules only. See the Chapter 11 of the LANplex® 2500 Operation Guide for more information about the ATM protocol. See the LANplex® 2500 Administration Console User Guide for information about how to conﬁgure ATM ports.

Interface

Characteristics

Each IP interface has the following information associated with it:

■ IP Address — This address, which is speciﬁc to your network, should be

chosen from the range of addresses assigned to your organization by the central agency. This address deﬁnes both the number of the network to which the interface is attached and the inter face’s host number on that network.

■ Subnet Mask — A subnet mask is a 32-bit number that uses the same

format and representation as IP addresses. The subnet mask determines which bits in the IP address are interpreted as the network number, the subnet number, and the host number. Each IP address bit corresponding to a 1 in the subnet mask is in the network/subnet part of the address. Each IP address bit corresponding to a 0 is in the host part of the IP address.

■ Advertisement Address — The switching module uses this IP address

when it advertises routes to other stations on the same subnet. In particular, the system uses this address for sending RIP updates. By default the switching module uses a directed advertisement (all 1s in the host ﬁeld).

■ Cost — This number, between 1 and 15, is used when calculating route

metrics. Unless your network has special requirements, assign a cost of 1 to all interfaces.

■ Type — The IP interface is one of these types:

■ VLAN, which supports routing between two VLANs

■ LIS, which supports classical IP over ATM

■ State — This status of the IP interface indicates whether the interface is

available for communications.

■ VLAN Interface — When you select VLAN as the interface type, the

Administration Console prompts you for the VLAN index number. The VLAN index number indicates which bridge ports are associated with the IP interface. When the LANplex Administration Console menu prompts you for

Administering interfaces 9-3

this option, the system displays a list of available VLAN indexes and the bridge ports associated with them.

■ LIS Interface — When you select LIS as the interface type, the

Administration Console prompts you for LIS interface information. The information you enter depends on whether you deﬁne permanent virtual circuits (PVCs), switched virtual circuits (SVCs), or both on the LIS interface. See the LANplex® 2500 Operation Guide for more information on PVCs and SVCs.

If you deﬁne SVCs, you need to enter an ATM ARP server address. This server maintains the IP-to-ATM address translation table. You can enter the maximum number of SVCs allowed on this interface. The minimum holding time determines the least amount of time an SVC connection remains open. The inactivity timer determines how long the connection can remain open with no activity after the minimum holding time has expired. You also need to enter the ATM port number for this interface.

If you deﬁne only PVCs on the interface, you need to enter only the PVC numbers and the ATM port number. The other prompts do not appear because you do not enter an ATM ARP server address. If you deﬁne both SVCs and PVCs, enter all LIS interface information.

Top-Level Menu

system

➧ interface

ethernet

route

fddi

arp

atm

atmArpServer

bridge

multicast

➧ ip

udpHelper

ipx

routing

appletalk

icmpRouterDiscovery

snmp

rip

analyzer

ping

script

statistics

logout

Displaying

Interfaces

➧ summary ➧ detail

define modify remove addAdvertisement removeAdvertisement addPVC removePVC

You can display both summary and detailed information about all IP interfaces conﬁgured for the system. The detail display contains all the summary information as well as information about the advertisement address, PVCs, and VLANs.

To display IP interface information, enter one of the following command strings from the Administration Console top-level menu:

ip interface summary

ip interface detail

9-4 CHAPTER 9: ADMINISTERING IP ROUTING

Example summary display:

IP routing is enabled, RIP is active, ICMP discovery is disabled.

Index Type IP address Subnet mask Cost State VLAN Index 1 VLAN 158.101.1.1 255.255.255.0 1 Down 2

Index Type IP address Subnet mask Cost State Port 2 LIS 158.101.112.1 255.255.255.0 1 Up 1

Example detail display:

IP forwarding is enabled, RIP is active, ICMP discovery is disabled.

Index Type IP address Subnet mask Cost State VLAN index 1 VLAN 158.101.1.1 255.255.255.0 1 Down 2

Index Type IP address Subnet mask Cost State Port 2 LIS 158.101.112.1 255.255.255.0 1 Up 1

4 Advertisement Addresses:

158.101.112.200 158.101.112.203 158.101.112.204 158.101.112.205

atmArpServer 47-0000-00-000000-0000-0000-00cc-080001200054-ff

maxSvcCount inactivityTime minHoldingTime 0 1200 60

1PVC: 1/32

Deﬁning an IP LIS

Interface

When you deﬁne an IP LIS interface, you specify several general IP interface characteristics and IP LIS characteristics.

Before you deﬁne an IP LIS interface with SVCs, be sure you have deﬁned an

Top-Level Menu

system

➧ interface

ethernet

route

fddi

arp

atm

atmArpServer

bridge

multicast

➧ ip

udpHelper

ipx

routing

appletalk

icmpRouterDiscovery

snmp

rip

analyzer

ping

script

statistics

logout

summary detail

➧ define

modify remove addAdvertisement removeAdvertisement addPVC removePVC

ATM ARP server as described in the section “Administering ATM ARP Ser vers” later in this chapter. If the LIS interface has only PVCs, you do not need to deﬁne an ATM ARP server.

To deﬁne an IP interface:

1 From the top level of the Administration Console, enter :

ip interface define

Administering interfaces 9-5

The Console prompts you for the interface’s parameters. To use the value in brackets, press [Return] at the prompt.

2 Enter the IP address of the interface. 3 Enter the subnet mask of the network to which the interface is to be

connected.

4 Enter the cost value of the interface. 5 Enter the type of IP interface: LIS. 6 Enter the advertisement addresses for this interface. You can enter up to 32

advertisement addresses for each interface. (The maximum number on the LANplex system is 64.)

7 Enter the LIS information:

■ For a LIS interface with SVCs, enter the ATM ARP server address, the

maximum SVC count, the inactivity timer, the minimum holding time, and the ATM port associated with the interface. (You can also accept the defaults for these values.)

■ For a LIS interface with only PVCs, enter the ATM port and the PVCs

associated with the interface. You can enter up to 51 PVCs for each interface. (The maximum number on the LANplex system is 64.)

LIS interface example with both PVCs and SVCs:

Enter IP address: 158.101.1.1 Enter subnet mask [255.255.0.0]: 255.255.255.0 Enter cost [1]:

Enter interface type (vlan,lis) [lis]: Enter advertisement address(es) []: Enter ATM arp server address [00-0000-00-000000-0000-0000-0000-000000000000-00]:

00000-00cc -000000000001-ff

Accept completed ATM address (yes,no) [yes]: Enter max. SVC count (0=no max.0) [0]: Enter inactivity time (0=infinite, 10-10000) seconds [1200]: Enter min. holding time (0-10000) seconds [60]: Select ATM port [1]: Enter PVC(s) (VPI/VCI)[]: 1/32,1/200,1/3330

158.101.112.1

47-0000-00-000000-000

9-6 CHAPTER 9: ADMINISTERING IP ROUTING

Deﬁning an IP

VLAN Interface

Top-Level Menu

system ethernet

➧ interface

fddi

route

atm

arp

bridge

atmArpServer

➧ ip

multicast

ipx

udpHelper

appletalk

routing

snmp

icmpRouterDiscovery

analyzer

rip

script

ping

logout

statistics

summary detail

➧ define

modify remove addAdvertisement removeAdvertisement addPVC removePVC

When you deﬁne an IP VLAN interface, you specify several interface characteristics, as well as the index of the VLAN associated with the interface.

You must ﬁrst deﬁne a VLAN, as described in Chapter 8, Administering VLANs, before you deﬁne an associated IP VLAN interface.

To deﬁne an IP VLAN interface:

1 From the top level of the Administration Console, enter :

ip interface define

The Console prompts you for the interface’s parameters. To use the value in brackets, press [Return] at the prompt.

2 Enter the IP address of the interface. 3 Enter the subnet mask of the network to which the interface is to be

connected.

4 Enter the cost value of the interface. 5 Enter the type of IP interface: VLAN. 6 Enter the advertisement address for this interface. 7 Enter the index of the VLAN associated with the interface.

Example:

Enter IP address: 158.101.1.1 Enter subnet mask [255.255.0.0]: 255.255.255.0 Enter cost [1]: Enter interface type (vlan, lis) [vlan]: Enter advertisement address(es) [158.101.1.255]: IP VLANs:

Index Ports 3 1-8 4 9-12

Select VLAN index: 3

If you physically change the conﬁguration of your system after deﬁning IP interfaces, the ports designated for those interfaces might no longer be valid and you might want to reconﬁgure your interfaces.

3COM CS 2500 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual