Avaya Bridging User Manual

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Page 1

Configuring Bridging Services

Router Software Version 10.0

Site Manager Software Version 4.0

Part No. 112950 Rev. A

January 1996

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recommendations in this document are believed to be accurate and reliable, but are presented without express or implied warranty. Users must take full responsibility for their applications of any products speciﬁed in this document. The information in this document is proprietary to Bay Networks, Inc.

The software described in this document is furnished under a license agreement and may only be used in accordance with the terms of that license. A summary of the Software License is included in this document.

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Bay Networks, Inc. does not assume any liability that may occur due to the use or application of the product(s) or circuit layout(s) described herein.

Portions of the code in this software product are Copyright © 1988, Regents of the University of California. All rights reserved. Redistribution and use in source and binary forms of such portions are permitted, provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that such portions of the software were developed by the University of California, Berkeley. The name of the University may not be used to endorse or promote products deri ved from such portions of the software without speciﬁc prior written permission.

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In addition, the program and information contained herein are licensed only pursuant to a license agreement that contains restrictions on use and disclosure (that may incorporate by reference certain limitations and notices imposed by third parties).

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Bay Networks Software License

Note:

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Bay Networks Software License

9. Licensee shall not reverse assemble, reverse compile, or in any way reverse engineer the Software. [Note: For licensees in the European Community, the Softw are Directiv e dated 14 May 1991 (as may be amended from time to time) shall apply for interoperability purposes. Licensee must notify Bay Networks in writing of any such intended examination of the Software and Bay Networks may provide review and assistance.]

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(continued)

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Bay Networks, Inc.

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About This Guide

If you are responsible for conﬁguring and managing Bay Networks routers, you should read this guide to learn how to customize Bay Networks router software for bridging services.

This guide,

• Transparent bridging services (Chapter 1)

• Source routing bridge services (Chapter 2)

• NetBIOS services (Chapter 3)

• Translation bridge services (Chapter 4)

• Native mode LAN (NML) services (Chapter 5)

Audience

Written for system and network managers, this guide presents information on how to conﬁgure the Bay Networks implementation of bridging interfaces to suit your environment.

Before Y ou Begin

Before using this guide, you must complete the following procedures:

• Create and save a conﬁguration ﬁle that has at least one bridging interface.

• Retrieve the conﬁguration ﬁle in local, remote, or dynamic mode.

Conﬁguring Bridging Services

, offers details on conﬁguring

• Reboot the router with the conﬁguration ﬁle. Refer to

Conﬁguring Routers

for instructions.

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Configuring Bridging Services

Bay Networks Customer Support

Bay Networks provides live telephone technical support to our distributors, resellers, and service-contracted customers from two U.S. and three international support centers. If you have purchased your Bay Networks product from a distributor or authorized reseller, contact the technical support staff of that distributor or reseller for assistance with installation, conﬁguration, troubleshooting, or integration issues.

Customers also have the option of purchasing direct support from Bay Networks through a variety of service programs. The programs include priority access telephone support, on-site engineering assistance, software subscription, hardware replacement, and other programs designed to protect your investment.

To purchase any of these support programs, including PhonePlus™ for 24-hour telephone technical support, call 1-800-2LANWAN. Outside the U.S. and Canada, call (408) 764-1000. You can also receive information on support programs from your local Bay Networks ﬁeld sales ofﬁce, or purchase Bay Networks support directly from your reseller. Bay Networks provides several methods of receiving support and information on a nonpriority basis through the following automated systems.

CompuServe

xviii

Bay Networks maintains an active forum on CompuServ e. All you need to join us online is a computer, a modem, and a CompuServe account. We also recommend using the CompuServe Information Manager software, available from CompuServe.

The Bay Networks forum contains libraries of technical and product documents designed to help you manage and troubleshoot your Bay Networks products. Software agents and patches are available, and the message boards are monitored by technical staff and can be a source for problem solving and shared experiences.

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Once you are online, you can reach our forum by typing the command GO BAYNETWORKS at any ! prompt.

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InfoFACTS is the Bay Networks free 24-hour fax-on-demand service. This automated system contains libraries of technical and product documents designed to help you manage and troubleshoot your Bay Networks products. The system can return a fax copy to the caller or to a third party within minutes of being accessed.

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About This Guide

(44) 272-760681.

Representative No. 591, or consult your listings for an ofﬁce near you.

Bay Networks maintains a WWW Home Page that you can access at http:// www.baynetworks.com. One of the menu items on the Home Page is the Customer Support Web Server, which offers technical documents, software agents, and an E-mail capability for communicating with our technical support engineers.

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For additional information or advice, contact the Bay Networks Technical Response Center in your area:

United States 1-800-2LAN-WAN Valbonne, France (33) 92-966-968 Sydney, Australia (61) 2-903-5800 Tokyo, Japan (81) 3-328-005

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Configuring Bridging Services

Conventions

This section describes the conventions used in this guide. angle brackets (< >) Indicate that you choose the text to enter based on the

arrow character (➔) Separates menu and option names in instructions.

description inside the brackets. Do not type the brackets when entering the command. Example: if command syntax is

192.32.10.12

Example: Protocols

<ip_address>

➔

AppleTalk identiﬁes the

, you enter

ping

AppleTalk option in the Protocols menu.

ping

bold text

Indicates text that you need to enter and command

dinfo

names in text. Example: Use the

command.

brackets ([ ]) Indicate optional elements. You can choose none, one,

or all of the options.

italic text

Indicates variable values in command syntax descriptions, new terms, ﬁle and directory names, and book titles.

quotation marks (“ ”) Indicate the title of a chapter or section within a book.

screen text

ellipsis points Horizontal (. . .) and vertical ellipsis points indicate

Indicates data that appears on the screen. Example:

Bay Networks Trap Monitor Filters

()

Set

omitted information.

vertical line (|) Indicates that you enter only one of the parts of the

command. The vertical line separates choices. Do not type the vertical line when entering the command.

Example: If the command syntax is

show at routes show at routes

nets

, you enter either

show at nets

, but not both.

Page 9

Ordering Bay Networks Publications

To purchase additional copies of this document or other Bay Networks publications, order by part number from Bay Networks Press™ at the following numbers. You may also request a free catalog of Bay Networks Press product publications.

Phone: 1-800-845-9523 FAX - U.S./Canada: 1-800-582-8000 FAX - International: 1-916-939-1010

Acronyms

APE all-paths explorer frame ARE all-routes explorer frame ARP Address Resolution Protocol BPDU Bridge Protocol Data Unit CUGID closed user group ID DA destination address DLCI data link connection identiﬁer DLSw data link switching DSAP destination service access point FCS frame check sequence FDDI Fiber Distributed Data Interface IEEE Institute of Electrical and Electronic Engineers IP Internet Protocol IPX Internet Packet Exchange LLC logical link control LNM LAN Network Manager MAC media access control MIB Management Information Base MTU Maximum Transmission Unit NetBIOS Network Basic Input/Output System NML Native Mode LAN OUI organizationally unique identiﬁer

About This Guide

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Configuring Bridging Services

PPP Point-to-Point Protocol RFC Request for Comments RIF Routing Information Field SA source address SAP service access point SMDS Switched Multimegabit Data Services SNAP Subnetwork Access Protocol SR source routing SRF speciﬁcally routed frame SSAP session service access point STE spanning tree explorer frame TB transparent bridging XNS Xerox Network System

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Using Transparent Bridge Services

This chapter contains information on the following topics:

• The transparent bridge, including an overview of the transparent bridge and details on how the spanning tree algorithm works

• Enabling bridge service and spanning tree on an interface

• Transparent bridge parameters, including information on how to edit the parameters using Conﬁguration Manager.

• Deleting the bridge and spanning tree from the router

Transparent Bridge Overview

Chapter 1

Transparent bridges are data-link layer relay devices that connect two or more networks. They use media access control (MA C) source and destination addresses to relay frames between connected networks.

Note:

We use the terms

throughout this chapter.

The transparent bridge provides three primary services:

• Learns the addresses of endstations on connected networks

• Forwards or drops frames based on knowledge it acquires about endstation addresses or user-conﬁgured ﬁlters

• Ensures a loop-free topology throughout the extended network, using the spanning tree algorithm

bridge

and

transparent bridge

interchangeably

1-1

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Configuring Bridging Services

A transparent bridge also provides some translation services, converting frames for bridging between Ethernet/802.3 LANs and Fiber Distributed Data Interface (FDDI) LANs. Refer to “The Translation Process” later in this chapter for details on translation services.

How the Bridge Works

The bridge receives and examines every frame transmitted on the networks to which it is attached. It learns endstation addresses by reading the source address of the endstation that transmitted the frame and noting which LAN interface received the frame. The bridge enters this information into a data structure called

forwarding table

the For example, in Figure 1-1, if Node 2 transmits a frame onto the network for the

ﬁrst time, the bridge receives the frame and makes an update to its forwarding table. The bridge notes that Node 2 is in the direction of LAN A.

, which the bridge constantly updates.

Forwarding Table

Node MAC Addr LAN

1-2

00:00:A2:00:00:01 00:00:A2:00:00:02

00:00:A2:00:00:03 00:00:A2:00:00:04

LAN A

Bridge

Node 1

MAC Address=

00:00:A2:00:00:01

Node 2

MAC Address=

00:00:A2:00:00:02 00:00:A2:00:00:03

Figure 1-1. Forwarding Table Update

A A

B B

MAC Address=

Update

Node 3

LAN B

Node 4

MAC Address=

00:00:A2:00:00:04

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Using Transparent Bridge Services

The bridge then forwards (relays to another network) or drops (discards) the frame based on the forwarding table entries. When the bridge receives a frame, it compares the frame’s destination address with addresses in the forwarding table. One of these situations results:

• If the frame’s destination address is on the same LAN as its source address, the bridge discards the frame; all nodes on that LAN already received this frame.

• If the frame’s destination address is on a different LAN than its source address, the bridge

forwards

the frame to that LAN.

• If there is no match for the frame’s destination address in the forwarding table, the bridge forwards the frame to all networks except the one that received the frame. This is called ﬂooding.

• If the frame is destined for the bridge (for example, a spanning tree frame), the bridge forwards the frame to the appropriate bridge entity and processes it internally .

Note:

If a frame is forwarded or ﬂooded to a LAN using a different data-link level protocol, the bridge translates the frame to the appr opriate frame format before transmission.

The T ranslation Process

The transparent bridge translates frames for bridging between Ethernet/802.3 LANs and FDDI LANs. When the transparent bridge receives Ethernet/802.3 frames destined for an FDDI LAN, it reformats those frames to the FDDI MAC frame format. The transparent bridge sets the original MAC frame type in the logical link control (LLC) header. Therefore, if the frame passes through a second, FDDI-to-Ethernet/802.3 bridge, that bridge can translate the frame back to its original format.

The bridge translates all Ethernet MAC frames to FDDI MAC and IEEE 802.2 LLC/Subnetwork Access Protocol (SNAP) encapsulation, as speciﬁed by RFC

1042. Protocols that adhere to RFC 1042 include DECnet Phase IV, Novell, AppleTalk Phase I and II, Xerox Network System (XNS), Internet Package Exchange (IPX), and Internet Protocol (IP).

Figure 1-2 shows the format and values of the LLC and SNAP headers of these frames after translation.

1-3

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Configuring Bridging Services

DSAP SSAP Control OUI Protocol Type

0 xAA 0 xAA 03 000000 (OriginalType)

Figure 1-2. RFC 1042 Encapsulation

AppleTalk Address Resolution Protocol (ARP) frames (Ethernet frames with a protocol type equal to 80F3) require special translation by the Bridge Tunnel Service.

Figure 1-3 illustrates the LLC and SNAP headers of the AppleT alk ARP outbound frame after the Bridge Tunnel Service translation.

DSAP SSAP Control OUI Protocol Type

0 xAA 0 xAA 03 0000F8 80F3

SNAP LLC

1-4

Key

SNAP = Subnetwork Access Protocol LLC = logical link control DSAP = destination service access point SSAP = session service access point OUI = organizationally unique identifier

Figure 1-3. Bridge Tunnel Service Encapsulation

The bridge translates all IEEE 802.2 LLC frames by removing the length ﬁeld. Protocols in this category include AppleTalk Phase 2, Novell Proprietary, and IP.

Figures 1-4 and 1-6 illustrate different LAN conﬁgurations and show how Bridge A translates different types of frames originating on LAN 1 for transmission across the FDDI LAN. Figure 1-5 shows how Bridge B translates frames transmitted from the FDDI LAN to LAN 2.

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Using Transparent Bridge Services

Ethernet LAN1 Ethernet LAN2

Bridge A

Bridge B

FDDI LAN

Ethernet to FDDI Translation

Through Bridge A to FDDI LANFrom Ethernet LAN

DA DA SASA

TYPE

=80F3

DATA FCS

SNAP LLC OUI

AA AA 03 00 00 00

Bridge A

• Extracts addressing information from the Ethernet header.

• Incorporates address information into newly generated FDDI MAC header.

• Encapsulates Ethernet data according to RFC 1042.

• Recalculates frame check sequence (FCS).

Ethernet (AppleTalk ARP) to FDDI Translation

From Ethernet LAN

DA SA

TYPE =80F3

DATA FCS

Through Bridge A to FDDI LAN

DA SA

SNAP LLC OUI

AA AA 03 00 00 F8

TYPE

=80F3

TYPE

=80F3

DATA

FCSDATA

FCS

Bridge A

• Extracts addressing information from the Ethernet header.

• Incorporates address information into newly generated FDDI MAC header.

• Encapsulates Ethernet data within an IEEE 802.2H-defined SNAP header that has an organizationally unique identifier (OUI) of 0000F8.

• Recalculates FCS.

Figure 1-4. Ethernet to FDDI Translation

1-5

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Configuring Bridging Services

Ethernet LAN1 Ethernet LAN2

Bridge A

Bridge B

FDDI LAN

FDDI to Ethernet Translation

From FDDI LAN

DA SA

SNAP LLC OUI

AA AA 03 00 00 00 =80F3

TYPE

FCSDATA

Through Bridge B to Ethernet LAN

Bridge B

• Extracts addressing information from the FDDI header.

• Incorporates address information into newly generated Ethernet MAC header.

• Removes RFC 1042 from Ethernet data.

• Recalculates frame check sequence (FCS).

FDDI to Ethernet (AppleTalk ARP) Translation

From FDDI LAN

DA SA

SNAP LLC OUI

AA AA 03 00 00 F8

TYPE

=80F3

DATA

FCS

Through Bridge B to Ethernet LAN

DA SA

TYPE =80F3

DATA FCS

Bridge B

• Extracts addressing information from the FDDI header.

• Incorporates address information into newly generated Ethernet MAC header.

• Removes Ethernet data from an IEEE 802.2H-defined SNAP header that has an organizationally unique identifier (OUI) of 0000F8.

• Recalculates FCS.

Figure 1-5. FDDI to Ethernet Translation

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Using Transparent Bridge Services

Ethernet LAN1 Ethernet LAN2

Bridge A Bridge B

FDDI LAN

802.3 to FDDI Translation

Through Bridge A to FDDI LANFrom 802.3 LAN

DA SA LEN DSAP SSAP CTL DATA FCS DA SA DSAP SSAP CTL DATA FCS

Bridge A

• Extracts addressing information from the 802.3 header.

• Incorporates address information into newly generated FDDI MAC header with no length (LEN) field.

• Encapsulates 802.3 data within FDDI frame.

• Recalculates FCS.

Figure 1-6. Ethernet/802.3 to FDDI Translation

The translation process from the FDDI LAN to Ethernet/802.3 LAN (the process Bridge B performs in Figures 1-5 and 1-6) is a mirror image of the translation process occurring on Bridge A, with one exception: the bridge translates an AppleTalk ARP frame that originates on the FDDI LAN and is destined for an Ethernet/802.3 LAN as shown in Figure 1-7.

1-7

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Configuring Bridging Services

AppleTalk ARP frame originating on FDDI LAN

DA SA

SNAP LLC OUI

AA AA 03 = 00 00 00

Through Bridge B to 802.3 LAN

DA SA

SNAP LLC OUI

LEN

AA AA 03 = 00 00 00

Bridge B

• Extracts addressing information from the FDDI MAC header

• Incorporates address information into newly generated 802.3 header

• Adds a length field

• Encapsulates FDDI data according to RFC 1042

• Recalculates FCS

Figure 1-7. AppleTalk ARP (Originating on FDDI) to 802.3 Translation

Spanning T ree Algorithm

TYPE

=80F3

TYPE

=80F3

DATA

FCS

DATA FCS

1-8

The spanning tree algorithm ensures the existence of a loop-free topology in networks that contain parallel bridges. (Refer to

Standard 802.1d Media Access Contr ol (MAC) Bridges

Source Routing Appendix to IEEE

for details on the spanning tree algorithm.) A loop occurs when there are alternate routes between hosts. If there is a loop in an extended network, bridges may forward trafﬁc indeﬁnitely, which can result in increased trafﬁc and degradation in network performance.

Figure 1-8 shows an example of a network containing a loop: two parallel bridges, Bridge 1 and Bridge 2, connect LANs A and B.

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IF 9

BR 4

Using Transparent Bridge Services

LAN C

ES K

IF 5

ES J

IF 2

BR 2BR 1

IF 3

IF 6

LAN B

IF 1

IF 8

LAN A

Figure 1-8. Parallel Bridge Topology

When Endstation J initially sends a frame to Endstation K, both Bridge 1 and Bridge 2 read the frame. Since this is the ﬁrst frame sent between J and K, there is no forwarding table entry for J or K on either of the bridges. Each bridge updates its forwarding table to indicate that Endstation J is in the direction of LAN A. Then, each bridge ﬂoods the frame: Bridge 1 forwards the frame over Interface 1 and Bridge 2 forwards the frame over Interface 2. Bridge 2 also forwards the frame over Interface 3; however, to simplify the example, we do not trace this frame.

LAN D

Key

IF = Interface BR = Bridge

ES = Endstation

IF 7

IF 4

BR 3

1-9

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Configuring Bridging Services

Next, Endstation K receives tw o copies of the frame, resulting in an inefﬁcient use of the available bandwidth. More serious, however, is the effect of duplicate frames on the two bridges. The frame ﬂooded by Bridge 1 onto Interface 1 is ultimately read by Bridge 2 on Interface 2. When Bridge 2 reads this frame, it updates its forwarding table to indicate that Endstation J is in the direction of LAN B. Similarly, Bridge 1 reads the frame ﬂooded by Bridge 2 and updates its forwarding table to show that Endstation J is in the direction of LAN B. Consequently , the forwarding tables of both bridges are no w corrupted and neither bridge can properly forward a frame to Endstation J.

You can avoid this problem by implementing the spanning tree algorithm, which produces a logical tree topology out of any arrangement of bridges. The result is that a single path exists between any two endstations on an extended netw ork. The spanning tree algorithm also provides a high degree of fault tolerance. It allows the network to automatically reconﬁgure the spanning tree topology if there is a bridge or data-path failure.

The spanning tree algorithm requires ﬁve values to derive the spanning tree topology. The ﬁrst, a multicast address specifying all bridges on the extended network, is media-dependent and is automatically determined by the software. You assign the remaining four values, which are

1-10

• Network-unique identiﬁer for each bridge on the extended network

• Unique identiﬁer for each bridge/LAN interface (called a port)

• Priority specifying the relative priority of each port

• Cost for each port After you assign these values, bridges multicast and process the formatted frames

(called Bridge Protocol Data Units, or BPDUs) to derive a single loop-free topology throughout the extended network. The bridges exchange BPDU frames quickly, minimizing the time that service is unavailable between hosts.

In constructing a loop-free topology, the bridges within the extended network follow these steps:

Elect a root bridge.

The bridge with the lowest priority value becomes the root bridge and serves as the root of the loop-free topology. If priority values are equal, the bridge with the lowest bridge MAC address becomes the root bridge.

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IF 3

Bridge A

Using Transparent Bridge Services

Determine path costs.

The path cost is the cost of the path to the root bridge offered by each bridge port.

Select a root port and elect a designated bridge on each LAN.

Each bridge designates the port that offers the lowest-cost path to the root bridge as the root port. In the event of equal path costs, the bridge examines the paths’ interfaces to the root bridge. The port (interface) of the path with the lowest interface priority to the root bridge becomes the root port. For example, Figure 1-9 shows how Bridge A determines its root port.

Given:

Root Bridge

IF 1

IF 2

LAN A

LAN B

IF 4

Path costs from IF 3 to root bridge and from IF 4 to root bridge are equal.

---------AND-------IF 1 = priority 1

IF 2 = priority 2 IF 3 = priority 3 IF 4 = priority 4

Then:

IF 3 becomes root port because IF 1’s priority is lower than IF 2’s

priority.

Figure 1-9. Root Port Determination (Equal Path Costs)

If the paths’ interfaces to the root bridge are also equal, then the root port is the port on the bridge with the lowest priority value (Figure 1-10).

1-11

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Configuring Bridging Services

Given: Path costs from IF 3 to root bridge and

from IF 4 to root bridge are equal.

---------AND-------IF 1 = priority 1

IF 2 = priority 1 IF 3 = priority 3 IF 4 = priority 2

Then:

IF 4 becomes root port because it has a higher priority than IF 3.

Same priority

IF 3

Bridge A

Root Bridge

IF 1

IF 2

LAN A

LAN B

IF 4

Figure 1-10. Root Port Determination (Equal Path Costs and Root Interface Priorities)

The spanning tree algorithm selects a bridge on each LAN as the designated bridge. The root port of this bridge has the lowest-cost path to the root bridge. All bridges turn off (set to blocking state) all of the lines except for the single line that is the shortest-cost path to the root and any line attached to the LANs for which the bridge serves as a designated bridge.

1-12

Elect a designated port.

The spanning tree algorithm selects the port that connects the designated bridge to the LAN as the designated port. If there is more than one such port, the spanning tree algorithm selects the port with the lowest priority as the designated port. This port, which carries all extended network trafﬁc to and from the LAN, is in the forwarding state.

Thus, the spanning tree algorithm removes all redundant ports (ports providing parallel connections) from service (places in the blocking state). If there is a topological change or a bridge or data-path failure, the algorithm derives a new spanning tree that may move some ports from the blocking to the forwarding state.

For example, in Figure 1-8, if all path costs are equal and Bridge 2 has the lowestbridge priority (followed by Bridge 3, Bridge 4, and Bridge 1), the spanning tree algorithm may block Bridge 1/Interface 8 and Bridge 4/Interface 9 from service.

Figure 1-11 shows the resulting logical topology, which provides a loop-free topology with only a single path between any two hosts.

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BR 2

Using Transparent Bridge Services

LAN B LAN A

IF 1

BR 4BR 1

Given: All path costs are equal.

Interface (IF) number denotes its priority.

----And----

BR 2 = priority 1 BR 3 = priority 2

BR 4 = priority 3 BR 1 = priority 4

IF 2 IF 3

IF 5

Then: Bridge 1/Interface 1 is blocked.

Bridge 4/Interface 5 is blocked.

Result: Loop-free topology

is created.

IF 6

LAN D

IF 7

BR 3

IF 8

LAN C

Figure 1-11. Spanning Tree (Loop-Free) Logical Topology

It is very important to conﬁgure the spanning tree parameters correctly. Consider the typical ﬂow of trafﬁc so that the logical topology that results from the spanning tree algorithm is appropriate for the network.

If, in the network shown in Figure 1-8, a majority of trafﬁc originates on LAN A and is destined for LAN D, it is not practical to set the spanning tree parameters as shown in Figure 1-12. This ﬁgure illustrates an inefﬁcient spanning tree topology for this network because the trafﬁc from LAN A must traverse Bridge 1, LAN B, and Bridge 2 to get to LAN D. LAN B is then congested with unnecessary trafﬁc.

1-13

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Configuring Bridging Services

BR 4

IF 5 IF 9

LAN B LAN C

BR 1

Given:

All path costs are equal.

Interface (IF) number

denotes its priority.

----And---BR 4 = priority 1

BR 3 = priority 2 BR 2 = priority 3 BR 1 = priority 4

Figure 1-12. Inefﬁcient Spanning Tree Topology

Filtering Frames

IF 1

IF 8

LAN A

IF 2

BR 2

IF 3

LAN D

Then:

Bridge 2/Interface 2 is blocked.

Bridge 3/Interface 7 is blocked.

Result: Inefficient spanning

tree topology is created.

IF 7

BR 3

1-14

You use ﬁlters mainly for security reasons. They enable the bridge to relay or drop a particular frame based on user-selectable ﬁelds within each of the four encapsulation methods supported by the bridge. These encapsulation methods are

• Ethernet

• IEEE 802.2 LLC

• IEEE 802.2 LLC with SNAP header

• Novell proprietary

Page 25

Using Transparent Bridge Services

Refer to ﬁlters and how to conﬁgure them for the bridge.

Conﬁguring Trafﬁc Filters and Protocol Prioritization

Enabling Bridge Service

This section describes how to enable bridge service and, optionally, spanning tree on an interface. It assumes you have read

1. Opened a conﬁguration ﬁle.

2. Speciﬁed router hardware if this is a local mode conﬁguration ﬁle.

3. Selected the link or net module connector on which you are enabling bridge

service, or conﬁgured a WAN circuit if this connector requires one.

Enabling Bridge Service on an Interface

To enable bridge service without spanning tree, select Bridge from the Select Protocols menu and click on OK. The Select Protocols menu appears after you either select a link or net module connector, or ﬁnish conﬁguring a WAN circuit.

When you enable bridge service without spanning tree, you need not specify any conﬁguration information, because Conﬁguration Manager supplies default values for the bridge parameters. The protocol pop-up window for the next enabled protocol appears, or, if only bridge is enabled on this circuit, the Bay Networks Conﬁguration Manager window appears. To edit the default values for the bridge parameters, refer to “Editing Bridge Parameters” for instructions.

Conﬁguring Routers

for details about

and that you have

Enabling Spanning Tree on an Interface

To enable spanning tree on an interface, use the following procedure.

1. From the Select Protocols menu, select the Spanning Tree option that is

directly under the Bridge option.

Note that the Conﬁguration Manager also selects the Bridge option because this Spanning Tree protocol cannot run without Bridge enabled.

2. Click on OK.

The Spanning Tree Autoconﬁguration window appears (Figure 1-13).

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Configuring Bridging Services

When you enable spanning tree service, you need only conﬁgure the Bridge Priority and Bridge MAC Address parameters. The Conﬁguration Manager supplies default values for the remaining parameters. If you want to edit the default values, see “Editing Bridge Parameters” later in this section.

Note: Because the spanning tree is global (that is, it runs across all Bridge

circuits), the Conﬁguration Manager only displays the Spanning Tree Autoconﬁguration window the ﬁrst time you specify Spanning Tree for the Bridge. If you have previously speciﬁed Spanning Tree for source routing, this window will not appear. To change the parameter settings at a later time, r efer to the “Editing Bridge Parameters” section.

3. Conﬁgure the parameters, using the descriptions that follow as a guide.

4. When you have conﬁgured the required parameters, click on OK.

A pop-up window prompts

Do you want to edit the Spanning Tree Interface Details?

5. Click on Cancel to enable default Spanning Tree service and display the

next protocol-speciﬁc pop-up window, or click on OK to edit the default spanning tree values.

1-16

(Refer to “Editing Bridge Parameters” for instructions.)

Page 27

Using Transparent Bridge Services

Figure 1-13. Spanning Tree Autoconﬁguration Window

Parameter: Bridge Priority

Default: 128

Range: 0 to 65535

Function: Combined with the Bridge MAC Address parameter, assigns a 64-bit

bridge ID to the router. This parameter supplies the most signiﬁcant 16 bits of the bridge ID, while Bridge MAC Address supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowest bridge ID number. Thus, the lower the value you set for this parameter, the more likely it is that the router will be selected as the root bridge.

Instructions: Enter a decimal value from 0 to 65535.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.5

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Configuring Bridging Services

Parameter: Bridge MAC Address

Default: Defaults to a unique MAC address that the router automatically creates

based on the router’s backplane ID.

Options: Any valid 48-bit MAC-level address

Function: Combined with the Bridge Priority parameter, assigns a 64-bit bridge ID

to the router. Bridge Priority supplies the most signiﬁcant 16 bits of the bridge ID, while this parameter supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowest bridge ID number. Thus, the lo wer the setting of Bridge Priority, the more likely it is that the router will be selected as the root bridge. In the event of equal Bridge Priority values, the value of this parameter determines the bridge’s priority.

Instructions: Enter a 48-bit MAC address expressed as a 12-digit hexadecimal value.

We recommend that you set this parameter to the MAC address of one of the router’s spanning tree ports, preferably the one with the lowest priority.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.5

Editing Bridge Parameters

Once you conﬁgure a circuit to support the bridge and, optionally, the spanning tree algorithm, you use Conﬁguration Manager to edit the bridge and spanning tree parameters.

This section provides information on how to access and edit these parameters.

Note: If you enable the spanning tree algorithm for your network, the

algorithm reconverges if you dynamically change any of the parameters described in the following sections.

You access all bridge parameters from the Conﬁguration Manager window (Figure 1-14). (Refer to Using Site Manager Software guide for details on accessing this window.)

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Using Transparent Bridge Services

Figure 1-14. Conﬁguration Manager Window

For each bridge and spanning tree parameter, this section provides information about default settings, valid parameter options, the parameter function, instructions for setting the parameter, and the Management Information Base (MIB) object ID.

Technician Interface lets you modify parameters by issuing commands that specify the MIB object ID. This process is equivalent to modifying parameters using Site Manager. For more information about using the Technician Interface to access the MIB, refer to Using Technician Interface Software.

Caution: The Technician Interface does not verify that the value you enter for

a parameter is valid. Entering an invalid value can corrupt your conﬁguration.

Editing Bridge Global Parameters

To edit the bridge global parameters:

1. Select Protocols➔Bridge➔Global from the Conﬁguration Manager

window (refer to Figure 1-14).

set and commit

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Configuring Bridging Services

The Edit Bridge Global Parameters window appears (Figure 1-15).

Figure 1-15. Edit Bridge Global Parameters Window

Edit the parameters, using the descriptions in the next section as a guide.

3. Click on OK to save your changes and exit the window.

Site Manager returns you to the Conﬁguration Manager window.

Bridge Global Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Edit Bridge Global Parameters window (refer to Figure 1-15).

Parameter: Enable

Default: Enable

Options: Enable

Function: Enables or disables bridging on the entire router.

Instructions: Set to Disable if you w ant to disable bridging for all circuits on the router.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.1.1.2

1-20

| Disable

Page 31

Parameter: Bridge Table Size

Default: 1024 entries

Using Transparent Bridge Services

Options: 1024

Function: Speciﬁes the maximum number of MAC address entries allowed in the

Instructions: Specify the table size, after accounting for the number of protocols

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.1.1.5

| 2048 | 4096 | 8192 | 16384 | 32768 | 65536 | 131072

forwarding table. If you enter an invalid value, the system rounds up or down from the invalid value to the nearest valid value.

If you increase the number of table entries, the bridge is more efﬁcient but uses more memory.

If you save a change to this parameter in dynamic mode, the bridge disables and then re-enables itself, thereby deleting all previously learned addresses.

running on your router and the size of the bridged network. The translation bridge, if conﬁgured, also adds addresses to this forwarding table. Therefore, if you conﬁgure the translation bridge, remember to account for the number of addresses it learns from the source route network.

Select the 131072 option only if the router is running IP Host Only and no other protocols are running on the router. If you select 131072, the system automatically disables the next parameter, Enable Forwarding DB.

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Configuring Bridging Services

Parameter: Enable Forwarding DB

Default: Enable

Options: Enable

Function: If you enable this parameter, the bridge maintains an additional table,

equal in size to the forwarding table plus dynamically allocated memory for each MAC address. This additional table contains each MAC address in the forwarding table and the port from which the bridge learned the address. The table allows you to access MAC addresses and ports via the MIB.

If you change the setting of this parameter in dynamic mode, the bridge disables and re-enables itself. If you change the setting to Disable, the bridge deletes all previously learned addresses, including those in the forwarding table.

Instructions: Leave this parameter enabled if you want to view the MAC addresses in

the forwarding table or the ports from which the bridge learned the addresses.

Disable this parameter if you need to improve bridge performance.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.1.1.6

| Disable

Editing Bridge Interface Parameters

To edit bridge interface parameters:

1-22

1. Select Protocols➔Bridge➔Interfaces from the Conﬁguration Manager

window (refer to Figure 1-14).

The Bridge Interfaces window appears (Figure 1-16).

Page 33

Using Transparent Bridge Services

Figure 1-16. Bridge Interfaces Window

Select the interface you want to edit.

3. Edit the parameters, using the descriptions in the next section as a guide.

4. Click on Apply to save your changes.

5. Click on Done to exit the window.

Site Manager returns you to the Conﬁguration Manager window.

Bridge Interface Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Bridge Interfaces window (refer to Figure 1-16).

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Configuring Bridging Services

Parameter: Enable

Default: If you added bridging using either the Quick-Start procedure or the

conﬁguring-circuits procedure, this parameter defaults to Enable. If you previously used this parameter to disable bridging on this circuit, the parameter defaults to Disable.

Options: Enable

Function: Toggles bridging on and off for this circuit only.

Instructions: This parameter does not allow you to add bridging to this circuit. To add

the bridging protocol to this circuit, you must use the Conﬁguration Manager (see Conﬁguring Routers).

Set this parameter to either Enable or Disable.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.3.1.2

Parameter: Translational Bridge Enable

Default: Disable

Options: Enable

Function: Speciﬁes whether this transparent bridge interface participates in a

transparent-to-source-routing translation-bridged network. Make sure you enable only one interface for translation bridging and that you disable this parameter for all other interfaces. Otherwise, translation bridging does not occur.

Instructions: Set this parameter to Enable or Disable, depending on your interface.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.3.1.9

| Disable

Editing Spanning Tree Global Parameters

To edit the spanning tree global parameters:

1. Select Protocols➔Bridge➔Spanning Tr ee➔Global from the

Conﬁguration Manager window (refer to Figure 1-14).

The Edit Spanning Tree Global Parameters window appears (Figure 1-17).

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Using Transparent Bridge Services

Figure 1-17. Edit Spanning Tree Global Parameters Window

Edit the parameters, using the descriptions in the next section as a guide.

3. Click on OK to save your changes and exit the window.

Site Manager returns you to the Conﬁguration Manager window.

Spanning Tree Global Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Edit Spanning Tree Global Parameters window (refer to Figure 1-17).

Parameter: Enable

Default: Enable

Options: Enable

Function: Enables or disables spanning tree on the entire router.

Instructions: Set to Disable if you want to disable spanning tree for the entire router, or

to Enable if you want to enable spanning tree for the entire router.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.2

| Disable

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Configuring Bridging Services

Parameter: Bridge Priority

Default: 128

Range: 0 to 65535

Function: Combined with the Bridge MAC Address parameter, assigns a 64-bit

bridge ID to the router. This parameter supplies the most signiﬁcant 16 bits of the bridge ID, while Bridge MAC Address supplies the remaining (least signiﬁcant) 48 bits.

Instructions: Enter a decimal value from 0 to 65535.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.5

Parameter: Bridge MAC Address

Default: Defaults to a unique MAC address that the router automatically creates

based on the router’s backplane ID.

Options: Any valid 48-bit MAC-level address

Function: Combined with the Bridge Priority parameter, assigns a 64-bit bridge ID

to the router. Bridge Priority supplies the most signiﬁcant 16 bits of the bridge ID, while this parameter supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowest bridge ID number. Thus, the lo wer the setting of Bridge Priority, the more likely it is that the router will be selected as the root bridge. In the event of equal Bridge Priority values, the value of this parameter determines the bridge’s priority.

Instructions: Enter a 48-bit MAC address expressed as a 12-digit hexadecimal value.

We recommend that you set this parameter to the MAC address of one of the router’s spanning tree ports, preferably the one with the lowest priority.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.5

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Using Transparent Bridge Services

Caution: We recommend that you not change the following three spanning

tree parameters (Max Age, Hello Time, and Forward Delay) unless absolutely necessary. However, if you do change them, you must follow these guidelines:

2 x (Forward Delay – 1 Second) ≥ Max Age Max Age ≥ 2 x (Hello Time + 1 Second)

If the values for Max Age, Hello Time, and Forward Delay are not the same for each bridge in your network, the root bridge parameters rule the entire topology.

Parameter: Max Age

Default: 20 seconds (expressed in hundredths of a second: 2000)

Range: 6 to 40 seconds

Function: Speciﬁes the maximum number of seconds that the router considers

protocol information (BPDUs) valid. After this speciﬁed amount of time, the router times out and discards the information.

We recommend that you accept the default value; however, if you change it, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or specify a new value. Make sure to

express any new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.15

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Configuring Bridging Services

Parameter: Hello Time

Default: 2 seconds (expressed in hundredths of a second: 200)

Range: 1 to 10 seconds

Function: Speciﬁes the interval in seconds between BPDUs transmitted by the

bridge. BPDUs are periodic transmissions exchanged between bridges in the network to convey conﬁguration and topology change data.

We recommend that you accept the default value; however, if you change it, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or enter a new value. Make sure you enter

the new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.16

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Using Transparent Bridge Services

Parameter: Forward Delay

Default: 15 seconds (expressed in hundredths of a second: 1500)

Range: 4 to 30 seconds

Function: Speciﬁes the time in seconds that a circuit spends in the listening and

learning states. If you set this parameter to the minimum value, the spanning tree converges at its fastest rate.

As the spanning tree algorithm operates, it eventually places all circuits in either a forwarding (enabled) or blocking (disabled) state. In response to network topology changes, the spanning tree algorithm may change the state of speciﬁc circuits. To prevent network looping caused by sudden state changes, the spanning tree algorithm does not change circuits directly from the blocking to the forwarding state. Rather, it places them in two intermediate states: listening and learning.

In the listening (standby) state, the circuit listens for network-generated BPDUs. It receives and drops all other trafﬁc. When the forward delay timer expires, the spanning tree algorithm places the circuit in the learning state.

In the learning state, the circuit receives both network-generated BPDUs and endstation-generated trafﬁc that is subjected to the learning process but is not relayed. When the forward delay timer expires, the spanning tree algorithm places the circuit in the forwarding state.

We recommend that you accept the default, 15 seconds; however, if you change the value, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or enter a new value. Make sure you enter

the new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.1.17

Editing Spanning Tree Interface Parameters

To edit spanning tree interface parameters:

1. Select Protocols➔Bridge➔Spanning Tr ee➔Interfaces from the

Conﬁguration Manager window (refer to Figure 1-14).

The Spanning Tree Interfaces window appears (Figure 1-18).

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Configuring Bridging Services

Figure 1-18. Spanning Tree Interfaces Window

Select the interface you want to edit.

3. Edit the parameters, using the descriptions in the next section as a guide.

4. Click on Apply to save your changes.

5. Click on Done to exit the window.

Site Manager returns you to the Conﬁguration Manager window.

Spanning Tree Interface Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters on the Spanning Tree Interfaces window (refer to Figure 1-18).

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Using Transparent Bridge Services

Parameter: Enable

Default: If you added spanning tree using either the Quick-Start procedure or the

conﬁguring-circuits procedure, this parameter defaults to Enable. If you previously used this parameter to disable spanning tree on this circuit, the parameter defaults to Disable.

Options: Enable

Function: Toggles spanning tree on and off for this circuit only.

Instructions: This parameter does not allow you to add spanning tree to this circuit. To

add the spanning tree to this circuit, you must use the Conﬁguration Manager. (Refer to Conﬁguring Routers for details.)

Instructions: Set this parameter to Enable or Disable.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.2.1.2

Parameter: Priority

Default: 128

Range: 0 to 255

Function: Assigns a priority to a bridge port. This interface priority value and the

bridge ID (bridge priority + bridge MAC address) determine whether this port becomes the designated port when the spanning tree algorithm converges. The lower the priority value, the higher the priority, and the more likely it is that this port will be the designated port.

Instructions: Either accept the default value or enter a new value.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.2.1.4

| Disable

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Configuring Bridging Services

Parameter: Path Cost

Default: 1

Range: 1 to 65535

Function: When this port is the root port, the path cost is the contribution of the path

through this port to the total cost of the path to the root for this bridge. When this port is not the root port, the path cost is added to the designated cost for the root port and is used as the value of the root path cost offered in all conﬁguration BPDUs transmitted by the bridge.

To determine the path cost, use this formula: Interface Path Cost = 1000/Attached LAN speed in Mb/s

Instructions: Enter a path cost value. For example, enter 100 if the attached LAN is

Ethernet (1000/10 = 100).

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.2.2.1.7

Flushing the Forwarding Table

You can clear (ﬂush) all MAC addresses from the bridge’s forwarding table without bringing the bridge down and back up. This function is only available when you conﬁgure the bridge in dynamic mode.

To ﬂush the tables, select Protocols➔Bridge➔Flush FWD Tables from the Conﬁguration Manager window (refer to Figure 1-14). The system unlearns all MAC addresses it previously stored in its forwarding table and then displays a conﬁrmation message.

Deleting the Bridge and Spanning Tree from the Router

To delete the bridge or spanning tree from all Bay Networks router circuits on which you enabled them, begin at the Conﬁguration Manager window (refer to Figure 1-14):

1. To delete the bridge and spanning tree, select Protocols➔Bridge➔Delete

Bridge. To delete the spanning tree only, select Protocols➔Bridge➔Spanning T r ee➔Delete Spanning Tree.

A conﬁrmation window appears asking whether you really want to delete the bridge or spanning tree.

2. Click on OK.

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Using Transparent Bridge Services

Site Manager returns you to the Conﬁguration Manager window. The bridge and/or spanning tree is no longer conﬁgured on the Bay Networks

router.

1-33

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Page 45

Chapter 2

Using Source Routing Bridge Services

This chapter

• Contains an overview of source routing technology

• Describes how the Bay Networks source routing bridge works

• Includes a list of additional source routing reference material

• Lists implementation guidelines for adding source routing bridges to your

network

• Describes how to enable source routing services on an interface

• Describes how to edit source routing parameters and delete source routing

from the router

Source Routing Overview

Source routing networks consist of LAN segments connected by source routing bridges (Figure 2-1).

ES 1

Internal LAN ID = 100

Ring ID = 1

Group ID = FFF Bridge ID = A

Figure 2-1. Source Routing Network

Bridge A

Bridge B

Internal LAN ID = 102

Group ID = FFF Bridge ID = A

ES 1

2-1

Page 46

Configuring Bridging Services

Each LAN segment has a unique network-wide identiﬁcation number, or ring ID. Each source routing bridge also has an identiﬁcation number, or bridge ID, and a unique network-wide internal or virtual LAN identiﬁcation number, called an internal LAN ID.

For each Bay Networks source routing bridge in the network, you assign an additional routing identiﬁer called a group LAN ID. The group LAN ID serves as a routing information ﬁeld (RIF) placeholder and Bay Networks identiﬁer.

How Source Routing Differs from Transparent Bridging

The Bay Networks source routing bridge differs from the Bay Networks transparent bridge (described in Chapter 1) in two ways:

• Source routing bridges can tolerate multiple paths between endstations in an

extended network; transparent bridges require loop-free topologies.

• Source routing bridges require endstations to supply the bridging information

needed to deliver a frame to a destination; transparent bridges use forwarding tables.

How Endstations on a Source Routing Network Discover Routes

The following sections describe the three processes that endstations on a source routing network use to learn the routes to destinations: all-paths broadcast routing, spanning tree broadcast routing, and speciﬁc routing.

All-Paths Broadcast Routing

An endstation that is conﬁgured for all-paths broadcast routing generates multiple frames that traverse all paths between source and destination endstations. These frames are all-routes explorer (ARE) or all-paths explorer (APE) frames.

When an endstation receives an ARE frame, a bridge within the source routing network appends a routing designator that identiﬁes the incoming ring ID, internal LAN ID/bridge ID, and outgoing ring ID (Figure 2-2). For information on the spanning tree algorithm, refer to Chapter 1.

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Using Source Routing Bridge Services

Incoming Ring ID Internal LAN ID/Bridge ID Outgoing Ring ID

001A 100A 0020 data...

Figure 2-2. Source Routing Designator

After the bridge adds the routing designator, the other bridges send the frame out all ports (ﬂoods the frame). As a result, multiple copies of the same ARE frame can appear on a LAN, and the frame recipient can receive multiple copies of the frame (one copy for each possible path through the extended network).

Each ARE frame received by the destination endstation contains a unique sequenced list of routing designators tracing the frame’s path through the source routing network.

Note: In a looped topology, the originating bridge may receive the ARE

frame; the originating bridge discards the frame.

Spanning Tree Broadcast Routing

An endstation conﬁgured for spanning tree broadcast routing generates a single frame that follows a loop-free path from source to destination. This frame is a spanning tree explorer (STE).

When an endstation generates an STE frame, each bridge on the spanning tree forwards the frame onto all active (nonblocked) ports, except the port that received the frame. With spanning tree broadcast routing, one copy of the STE appears on each LAN and the frame recipient receives a single copy only.

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Configuring Bridging Services

Speciﬁc Routing

When an endstation receives an ARE or STE frame, it generates a single frame, called a speciﬁcally routed frame (SRF). The SRF tra verses a speciﬁc path back to the source endstation; it contains a list of routing designators that maps a path through the extended network from source to destination.

When an endstation receives an SRF, each bridge between the source and destination examines the list of routing designators. The bridge forwards the SRF only if the bridge itself is on the speciﬁed path. Otherwise, it ignores the frame. When the SRF reaches the original source endstation, that station removes the routing information and stores it in its internal routing table.

Once the endstations discover a route and store the information in their routing tables, the endstations send speciﬁcally routed frames across the source routed network (Figure 2-3).

ES 1

All-Paths Explorer or Spanning Tree Explorer

Specifically Routed Frame

ES 1

Specifically Routed Frame

ES 1

Figure 2-3. Route Discovery

Source Routing over IP Networks

The Bay Networks source routing bridge supports Internet Protocol (IP) encapsulation. IP encapsulation allows the source routing bridge to route frames

to endstations located across an IP backbone network. These frames use standard IP transmission services and a proprietary sequence

maintenance protocol that ensures error-free, in-sequence delivery of IP encapsulated frames. The IP network can consist of any standard IP equipment and media.

ES 2

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How IP Encapsulation Works

When you enable IP encapsulation on a source routing bridge (thus making it an IP encapsulating bridge), you assign a single ring ID to the entire IP backbone network. The source routing bridge assigns only a single route descriptor to the frame’s RIF to describe the entire internet, regardless of the IP network size that the frame traverses. Therefore, frames source routed over large IP networks can remain within maximum hop count restrictions.

Whenever a Bay Networks source routing bridge receives an explorer frame, the bridge sends it toward an IP encapsulating bridge, which resides at the edge of the IP backbone network. (For example, in Figure 2-4, Bridges A, B, and C are IP encapsulating bridges.) The IP encapsulating bridge encloses the source routed frame within an IP header before it sends the frame out onto the network. When the frame reaches a peer IP encapsulating bridge, the bridge removes the encapsulation from the frame and sends it out the appropriate source routing interfaces.

Each IP encapsulating bridge maintains a dynamic mapping of destination IP addresses to the ring and bridge IDs of their directly attached rings. When an IP encapsulating bridge receives a source routed frame, it performs these steps:

Using Source Routing Bridge Services

1. Checks the frame’s RIF for the ring and bridge ID that immediately follow the

IP network ring and bridge ID in the RIF.

2. Looks up the IP address that corresponds with this ring and bridge ID.

3. Encapsulates the frame in an IP packet with the destination IP address.

4. Sends the frame out onto the IP network. For example, Figure 2-4 shows the IP mapping table for IP Encapsulating

Bridge A.

2-5

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Configuring Bridging Services

IP Explorer List Bridge A

1.1.2.2

1.1.3.3

for redundancy

1.1.5.5

1.1.1.1

Bridge A

IP Explorer List Bridge B

1.1.1.1

1.1.5.5

IP Network

Ring ID = 2

1.1.2.2 1.1.3.3

Bridge B

Bridge D

IP Explorer List Bridge C

1.1.1.1

1.1.2.2

1.1.3.3

Bridge C

1.1.5.5

IP Mapping Table for Bridge A

Ring ID Bridge ID IPAddress 3 C 1.1.5.5 4 B 1.1.2.2 5 B 1.1.3.3

6 B (Outgoing IP Interface to the IP Network Address on Bridge B. IP chooses the IP interface with the IP routing protocol.)

Note that you can reach Ring 7 by normal SRB from Bridge B.

Figure 2-4. Source Routing over an IP Network

2-6

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Using Source Routing Bridge Services

When Bridge A receives a source routed frame destined for an endstation on Ring 4, it examines the frame’s RIF and locates the next ring ID (4) that immediately follows the IP network ring ID (2), as shown in Figure 2-5.

IP Network Ring ID

Next Ring ID

MAC

RIF of an IP Encapsulated Frame

Source IP Address

1.1.1.1

RIF of an IP Encapsulated Frame

Figure 2-5. Examining the RIF Field of an SRF

001A 100A data... 0040

Destination IP Address

1.1.2.2

MAC

002B

001A 002A FFFA

Bridge A also e xamines the RIF to locate the bridge ID associated with the remote bridge used to reach Ring 4 (in this case, Bridge B). Then, Bridge A checks its mapping table for the IP address that corresponds to Ring ID 4 and Bridge B, and encapsulates the frame with an IP header. The IP header speciﬁes its own source address, and the proper IP destination address (1.1.2.2). Finally, Bridge A forwards the packet onto the IP network.

0040

data...

You control which IP interfaces receive explorer frames by deﬁning an IP Explorer list for each IP encapsulating bridge. For example, all of the IP

encapsulating bridges that border the IP cloud in Figure 2-4 have IP explorer lists deﬁned. Each bridge forwards explorer packets that are in its individual list toward the IP addresses. Note that the IP explorer lists for each bridge can vary. This allows you to control which IP networks receive explorer trafﬁc.

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Configuring Bridging Services

IP Encapsulation Features

Bay Networks implementation of IP encapsulation allows you to:

• Conﬁgure redundant IP interfaces.

You can conﬁgure redundant IP interfaces on the same router for critical network connections (for example, interfaces 1.1.2.2 and 1.1.3.3 on Bridge B). That way, if you disable one of the interfaces, the other interface can still accept IP trafﬁc for the network. (When you enable redundant IP interfaces, you also increase explorer trafﬁc on the network. Therefore, enable redundant interfaces selectively to reduce the impact on your network performance.)

• Expand your IP backbone network.

You can expand your IP backbone to include any Bay Networks IP router on the network. You specify the router’s IP address in the IP explorer list for each bridge.

For example, Bridge A currently forwards all trafﬁc destined for Ring 7 to IP interface 1.1.3.3. That router then forwards the trafﬁc toward Ring 6 so that the router can source route it to Ring 7. If you add IP address 1.1.4.4. to the IP Explorer list for Bridge A, then Bridge A forwards all trafﬁc destined for Ring 7 directly to IP interface 1.1.4.4. By expanding your IP backbone, the source routing bridge can route through more stations, but it still can only add a single hop to a packet’s RIF.

2-8

• Reduce excess broadcast trafﬁc on your IP network.

You can reduce the number of broadcast and explorer packets that traverse the network by constructing directed explorer ﬁlters. (Refer to Conﬁguring Trafﬁc Filters and Protocol Prioritization for information on how to create ﬁlters that forward IP explorer frames to speciﬁc addresses.)

• Conﬁgure both IP encapsulation support and source route endstation support

on the same interface. IP encapsulation support works independently of source route endstation

support. However, you can enable both on the same circuit.

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Source Route Endstation Support

The Bay Networks routers running IP, IPX, XNS, AppleTalk, and VINES protocols support support routing over Token Ring networks that contain one or more source routing bridges. This feature is called source route endstation support.

In a source routing network, every endstation that sends out a frame supplies the frame with the necessary route descriptors so that the router can source route it across the network. Thus, for routers to route packets across a source routing network, they must act like endstations; the routers must supply route descriptors for each packet before they send it out onto the network.

When you enable end-node support and a Bay Networks router running IP, IPX, XNS, AppleTalk, or VINES receives a packet and determines that the packet’s next hop is across a source routing network, the router performs these steps:

1. Adds the necessary RIF information to the packet’s MAC header

2. Sends the packet out onto the network where it is source routed toward the

next hop

Using Source Routing Bridge Services

When the peer router receives the packet from the Token Ring network, it strips off the RIF ﬁeld and continues to route the packet toward the destination network address (Figure 2-6).

You conﬁgure source route end-node support for each individual routing protocol on a per-circuit basis.

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Configuring Bridging Services

ES 1

Router 1 Router 2

WF ES1 SNAP IP DATA

Bridge A

Packet Sent from ES1

Bridge B

Source Route RIF

WF2 WF1

ES2 WF2

0830 001A 002B 0030

SNAPIPIP

DATA

SNAP

Packet Sent from Router 2

DATA

Packet Sent from Router 1

Figure 2-6. IP Routers Source Routing across a Token Ring Network

How the Bay Networks Source Routing Bridge Works

ES 2

2-10

This section shows examples of how the Bay Networks source routing bridge routes frames through a Token Ring network. It also describes how the source routing bridge routes frames across an IP backbone network (called IP encapsulation).

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Source Routing across a Token Ring Network

The Bay Networks source routing bridge handles incoming packets differently, depending on the source routing bridge’s position in the Token Ring network. To demonstrate, the following sections describe the routing information ﬁeld (RIF) of a frame as it moves back and forth between Endstation 1 (ES1) and Endstation 2 (ES2) (Figure 2-7).

Using Source Routing Bridge Services

Example A Example B

ES 1 Bridge A Bridge B Bridge C

Internal LAN ID = 100

Internal Group ID = FFF

Bridge ID = A

Internal LAN ID = 101

Internal Group ID = FFF

Bridge ID = A

Example C

Internal LAN ID = 102

Internal Group ID = FFF

Bridge ID = A

Figure 2-7. Tracking an Explorer Frame

First, we track the RIF of an explorer frame sent from ES1 to ES2. Then, we track the RIF of a speciﬁcally routed frame sent back from ES2 to ES1.

The size of the RIF is variable. It contains the routing information required to transmit the frame across the network.

Although the following examples show only the Bay Networks source routing bridge, other IBM-compatible source routing bridges can reside in the same network.

ES 2

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Configuring Bridging Services

How the Source Routing Bridge Handles Explorer Frames

This section provides instructions on how the Bay Networks source routing bridge handles explorer frames (AREs or STEs) sent from ES1 to ES2 (refer to Figure 2-7). Each bridge’s internal LAN ID, group LAN ID, and bridge ID is in hexadecimal format below the bridge.

• Example A describes the actions of the ﬁrst Bay Networks bridge.

• Examples B and C describe the actions of other Bay Networks bridges in the

explorer frame’s path.

Example A: First bridge to receive the explorer frame

The frame received by Bridge A from Ring 1 did not traverse any other bridges. This bridge adds the following information in the RIF before it transmits the frame toward Ring 2 (Figure 2-8):

• Incoming ring ID/bridge ID

• Internal LAN ID/bridge ID

• Outgoing ring ID/bridge ID 0

2-12

Examples B and C: Other bridges that receive the explorer frame

The explorer frame received by Bridges B and C contains internal LAN IDs and bridge numbers, indicating that this frame traversed at least one other Bay Networks bridge. These bridges perform the following steps in the RIF before transmitting the frame toward Rings 3 and 4 (Figure 2-8):

1. Remove the last internal LAN ID

2. Replace the incoming ring ID and bridge ID 0 with its own bridge ID

3. Add its own internal LAN ID/bridge ID

4. Add the outgoing ring ID/bridge ID 0

Page 57

ES2 ES1 8270 DSAP SSAP DATA

Frame received by Bridge A

ES2 ES1 8830 001A 100A 0020 DSAP SSAP DATA

Frame sent out by Bridge A onto Ring 2

Using Source Routing Bridge Services

Destination system MAC address Source system MAC address Routing control ﬁeld

Data

Incoming Ring ID/Bridge ID LAN ID/Bridge ID

Outgoing Ring ID/Bridge ID of 0

Incoming Ring ID/Bridge ID

LAN ID/Bridge ID Outgoing Ring ID/Bridge ID of 0

ES2 ES1 8A30 001A 002A 101A 0030 DSAP SSAP DATA

Frame sent out by Bridge B onto Ring 3

ES2 ES1 8C30 001A 002A 003A 102A 0040 DSAP SSAP DATA

Frame sent out by Bridge C onto Ring 4

Figure 2-8. Structure of an Explorer Frame

Incoming Ring ID/Bridge ID

LAN ID/Bridge ID Outgoing Ring ID/Bridge ID of 0

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Configuring Bridging Services

How the Source Routing Bridge Handles Speciﬁcally Routed Frames

This section describes how the Bay Networks source routing bridge handles speciﬁcally routed frames (SRFs) sent from ES2 to ES1. Depending on the bridge’s position in the network, the bridge handles the SRFs differently (Figure 2-9).

Example A Example B

ES 1 Bridge A Bridge B Bridge C

Internal LAN ID = 100

Internal Group ID = FFF

Bridge ID = A

Internal LAN ID = 101

Internal Group ID = FFF

Bridge ID = A

Example C

Internal LAN ID = 102

Internal Group ID = FFF

Bridge ID = A

Figure 2-9. Tracking a Speciﬁcally Routed Frame from ES2 to ES1

If there is only a single bridge ID in the RIF, then the Bay Networks bridge transmits the frame to the outgoing circuit without modiﬁcation. This is true only when the frame traverses a single Bay Networks bridge (or any combination of third-party bridges) between the source and destination endstation.

If there are multiple bridge IDs in the RIF, then:

• Example A describes the actions of a Bay Networks bridge if it is the ﬁrst

bridge to handle the SRF.

ES 2

2-14

• Example B describes the actions of a Bay Networks bridge if there are

multiple bridge IDs in the RIF , and the bridge is between the ﬁrst and last Bay Networks bridge to handle the SRF.

• Example C describes the actions of a Bay Networks bridge if there are

multiple bridge IDs in the RIF, and the bridge is the last Bay Networks bridge to handle the SRF.

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Using Source Routing Bridge Services

Example A: First of several bridges to receive the SRF

The frame received by Bridge C from Ring 4 did not traverse any other Bay Networks bridges (but there are multiple bridge IDs in the RIF, so it will eventually). This bridge performs the following steps in the RIF before it transmits the frame toward Ring 3 (Figure 2-10):

1. Changes the destination system’s MAC address at the beginning of the frame

to a Bay Networks group address. This address is C000A2FFFFFFx, where x is the bridge ID of the next Bay

Networks bridge speciﬁed by the RIF.

2. Removes its own internal LAN ID and inserts the group LAN ID before the

last incoming ring and bridge ID listed in the RIF (Figure 2-10). Eventually, the internal LAN ID of the last Bay Networks bridge along the

frame’s path replaces the group LAN ID.

3. Copies the destination system’s MAC address into the data portion of the

frame.

Example B: Between the ﬁrst and last bridges to receive the SRF

The frame received by Bridge B from Ring 3 traversed at least one other Bay Networks bridge. Howev er, this is not the last Bay Networks bridge that the frame must traverse. This bridge performs the following steps in the RIF before transmitting the frame toward Ring 2 (Figure 2-10):

1. Locates the bridge ID, which is at the end of the group address.

2. Changes the bridge ID at the end of the group address to the bridge ID of the

next Bay Networks bridge in the RIF. (Only if it differs from the v alue already in place. In this example, all bridge IDs are the same, so the frame is not modiﬁed.)

Example C: Last of several bridges to receive the SRF

The frame received by Bridge A is the last of several Bay Networks bridges traversed by the frame. This bridge performs the follo wing steps in the RIF before it transmits the frame toward Ring 1 (Figure 2-10):

1. Replaces the Bay Networks group address with the destination MAC address

that was saved to the data ﬁeld

2. Replaces the group LAN ID with its own internal LAN ID

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Configuring Bridging Services

Destination MAC address

Outgoing Ring ID/Bridge ID

LAN ID/Bridge ID Incoming Ring ID/Bridge ID of 0

ES1 ES2 0CB0 001A 002A 003A 102A 0040 DSAP SSAP DATA

Frame received by Bridge C

Bay Networks group address

Next Bridge ID Group LAN ID Copy of destination MAC address

C000A2FFFFFA ES2 0CB0 001A FFFA 002A 003A 0040 DSAP SSAP DATA ES1

Frame sent out by Bridge C onto Ring 3

Bay Networks group address Next Bridge ID

C000A2FFFFFA ES2 0CB0 001A FFFA 002A 003A 0040 DSAP SSAP DATA ES1

Frame sent out by Bridge B onto Ring 2

Saved destinatin MAC address

LAN ID/Bridge ID

ES1 ES2 0CB0 001A 100A 002A 003A 0040 DSAP SSAP DATA

Frame sent out Bridge A onto Ring 1

Figure 2-10. Structure of a Speciﬁcally Routed Frame from ES2 to ES1

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Source Routing across an IP Network

This section provides details on how IP encapsulation works by tracing a speciﬁcally routed frame as it is sent out from Endstation 1, traverses several bridges and an IP network, and ﬁnally arrives at Endstation 2 (Figure 2-11).

IP Network Ring ID = 2

ExampleA Example B Example C

Using Source Routing Bridge Services

ES1

1.1.1.1

Bridge A

Internal LAN ID = 100

Internal Group ID = FFF

Bridge ID =A

Bridge B

Internal LAN ID = 101

Internal Group ID = FFF

Bridge ID = A

1.1.2.2

Figure 2-11. Tracking an IP-Encapsulated Frame from ES1 to ES2

Note: At this point, assume that explorer packets have traversed the network

and identiﬁed the paths to all reachable interfaces.

To demonstrate IP encapsulation, this section traces a speciﬁcally routed frame as it is sent out from Endstation 1 and arrives at Endstation 2:

• Example A describes the actions of the ﬁrst Bay Networks bridge to handle

the SRF. This bridge encapsulates the frame with an IP header before it sends the frame out onto the IP network.

Bridge C

Internal LAN ID = 102

Internal Group ID = FFF

Bridge ID =A

ES2

• Example B describes the actions of a Bay Networks bridge that is in between

the ﬁrst and last Bay Networks bridges to handle the SRF. This bridge removes the IP header from the frame before it source routes the frame to the next bridge.

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Configuring Bridging Services

• Example C describes the actions of the last bridge of several Bay Networks

bridges to handle the SRF.

Example A: First of several bridges to receive the SRF

Bay Networks Bridge A is the ﬁrst to receive the frame from Ring 1. Bridge A performs the following steps in the RIF before it transmits the frame onto the IP network (Figure 2-12):

1. Removes its own internal LAN ID.

2. Inserts the group LAN ID before the last incoming ring and bridge ID listed in

the RIF (Figure 2-12). Eventually, the internal LAN ID of the last Bay Networks bridge along the

frame’s path replaces the group LAN ID.

3. Adds an IP header containing the destination address 1.1.2.2 onto the frame

and sends it toward the IP network.

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Using Source Routing Bridge Services

Destination MAC address

Incoming Ring ID/Bridge ID LAN ID/Bridge ID

Outgoing Ring ID/Bridge ID

ES2 ES1 0C30 001A 100A 002A 003A 0040 DSAP SSAP DATA

Frame received by Bridge A

Source IP address Destination IP address

Group LAN ID

1.1.1.1

1.1.2.2

ES2 ES1 0C30 001A 002A 003A FFFA 0040 DSAP SSAP DATA

Frame sent out by Bridge A onto the IP network (Ring 002)

Bay Networks group address Next Bridge ID

Copy of destination MAC address

C000A2FFFFFA ES1 0C30 001A 002A 003A FFFA 0040 DSAP SSAP DATA ES2

Frame sent out by Bridge B onto Ring 3

Saved destination MAC address LAN ID/Bridge ID

ES2 ES1 0C30 001A 002A 003A 102A 0040 DSAP SSAP DATA

Frame sent out Bridge C onto Ring 4

Figure 2-12. Structure of an IP-Encapsulated Frame from ES1 to ES2

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Configuring Bridging Services

Example B: Between the ﬁrst and last bridges to receive the SRF

Bay Networks Bridge B receives the frame from the IP network (Ring 2) and performs the following steps on the RIF before it transmits the frame toward Ring 3 (refer to Figure 2-12):

1. Strips the IP header from the packet.

2. Changes the destination system’s MAC address at the beginning of the frame

to a Bay Networks group address. This address appears as C000A2FFFFFFx, where x is the bridge ID of the

next Bay Networks bridge speciﬁed by the RIF.

3. Copies the destination system’s MAC address into the data portion of the

frame.

4. Locates the bridge ID, which is at the end of the group address, and sends it to

the bridge ID of the next Bay Networks bridge in the RIF.

Example C: Last of several bridges to receive the SRF

The last Bay Networks bridge to receive the frame performs the follo wing steps in the RIF before it transmits the frame toward Ring 4 (refer to Figure 2-12):

2-20

1. Replaces the Bay Networks group address with the destination MAC address

that was saved to the data ﬁeld.

2. Changes the group LAN ID to its own internal LAN ID.

Page 65

IP Encapsulation Guidelines

When using IP encapsulation, the following guidelines apply:

• Do not conﬁgure source routing on WAN links connecting the remote routers.

• Deﬁne IP addresses in the IP explorer list so that the source routing bridge can

send AREs to those addresses.

• Conﬁgure IP on the port. The IP address automatically resides in the routing

table.

• Deﬁne at least two IP address for each router in another router’ s ARE e xplorer

table. If the service provided by one token ring interface is disabled, the router can still forward AREs.

• Alternatively, you could conﬁgure a connectionless IP address on each router

and conﬁgure only the connectionless address. This would reduce explorer trafﬁc but would ensure that the IP address is up.

Note: Each IP address on a router that receives an ARE forwards the ARE

through all other source routed interfaces. This can cause duplicate AREs on the network, but it ensures redundancy if the service of any token ring interface is interrupted.

Using Source Routing Bridge Services

Source Routing over Frame Relay Networks

The Bay Networks source routing bridge supports source routing over Frame Relay networks, using RFC 1490 standard Frame Relay encapsulation and Bay Networks proprietary Frame Relay encapsulation.

To select proprietary or RFC 1490 standard Frame Relay encapsulation, use the Encapsulation Format parameter as described in the section “Source Routing Interface Parameter Descriptions” later in this chapter.

Source Routing over FDDI

The Bay Networks source routing bridge supports communications between Token Ring endstations and FDDI endstations, using standard native encapsulation and proprietary encapsulation. Use Bay Networks proprietary encapsulation if you want to communicate with a Version 7 router running source routing over FDDI.

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Configuring Bridging Services

To select proprietary or standard encapsulation, use the Encapsulation Format parameter as described in the section “Source Routing Interface Parameter Descriptions” later in this chapter.

For More Information about Source Routing

The following documents provide technical details on Source Routing Protocol implementation:

IBM T oken Ring Network Ar chitectur e Refer ence. Third Edition (SC3D-3374-D2). New Y ork: IBM Corporation, September, 1989.

Source Routing Appendix to IEEE Standar d 802.1d. Media Access Contr ol (MAC) Bridges. Project 802.5m - Draft 71991.

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

Implementation Notes

This section contains some basic guidelines for adding Bay Networks source routing bridges to your network. It also describes some of the conﬁguration features that may match your network requirements.

Assigning Bridge IDs, Internal LAN IDs, and Group LAN IDs

When you enable the source routing bridge on the router, you must specify its bridge ID and internal LAN ID. The source routing bridge uses these routing designators and the group LAN ID to source-route packets through the network. The following sections describe each of these routing designators in detail.

Bridge ID

The bridge ID is a standard source routing designator that identiﬁes a bridge in the network. When you assign the bridge ID, make sure you follow these guidelines:

• Assign the same bridge ID to all other Bay Networks source routing bridges

on the network unless the bridges operate in parallel.

• Assign bridge IDs to Bay Networks bridges that are unique among all bridges

on the network.

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• Assign to third-party routers bridge IDs that differ from Bay Networks source

If two or more Bay Networks bridges operate in parallel, you must assign different bridge IDs. You must also specify the other Bay Networks bridge ID in the entry list for each bridge.

For example, in Figure 2-13, Bay Networks Bridges A, C, and D all hav e the same bridge ID (A). However, because Bridges B and C operate in parallel, Bridge B has a different bridge ID (B). You specify this bridge ID (B) in the Bridge Entry list for Bridges A, C, and D. This ensures that the bridges know Bridge B is active on the network. Similarly, you specify the bridge ID (A) for Bridge B on the Bridge Entry list so that it knows Bridges A, C, and D are active on the network.

Bridge ID = 1

Using Source Routing Bridge Services

routing bridge IDs.

Internal LAN ID = 104

Internal Group ID = FFF

Bridge ID = B BN Bridge Entry = A

Bridge ID = 1

Third-party

Bridge

ES 1

Bridge A

Internal LAN ID = 100

Internal Group ID = FFF

Bridge ID = A BN Bridge Entry = B BN Bridge Entry = B BN Bridge Entry = B

Figure 2-13. Parallel Operation

Internal LAN ID = 101

Internal Group ID = FFF

Bridge ID = A

Bridge B

Bridge C Bridge D

Internal LAN ID = 102

Internal Group ID = FFF

Bridge ID = A

Third-party

Bridge

ES 2

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Configuring Bridging Services

Internal LAN ID

The internal LAN ID is a source routing designator that identiﬁes the virtual LAN on which frames travel. When you conﬁgure the Bay Networks source routing bridge, you must assign a globally unique internal LAN ID to each bridge on which you enabled source routing. For example, in Figure 2-13, Source Routing Bridges A, B, C, and D all have unique internal LAN IDs.

Group LAN ID

The group LAN ID is a Bay Networks proprietary routing designator that helps the source routing bridges in your network identify the last Bay Networks bridge in their path. When you conﬁgure the Bay Networks source routing bridge, make sure you follow these conﬁguration guidelines:

• Assign the same group LAN ID to all source routing bridges in the network.

• Assign a group LAN ID to all bridges in your network. This number must be

different from the LAN ID value assigned to any other bridges in the network.

Conﬁguring IP Encapsulation Support

2-24

IP encapsulation support allows you to source route frames between Bay Networks bridges over IP networks. When you enable IP encapsulation on the source routing bridge, make sure you follow these guidelines:

• Enable at least one IP interface on those routers through which you want to

source route packets. You can enable IP on any circuit on any slot on the router; it does not have to be the same circuit on which you enabled source routing. (Refer to Conﬁguring IP Services for details on enabling IP on a circuit.)

• Conﬁgure redundant IP interfaces on different slots on the same router if you

want the router to receive broadcasts for backup purposes. Alternatively, you could conﬁgure a connectionless IP address on each router

and conﬁgure only the connectionless address. This results in reduced explorer trafﬁc but ensures that the IP interface is always available.

• Enable source routing on the circuits of those bridges through which you want

to source route frames. (Refer to “Enabling Source Routing Services” for details on enabling source routing on a circuit.)

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Using Source Routing Bridge Services

• Specify a ring ID for the backbone IP network to which the source routing

interface connects. You enter the IP network’s ring ID using the Conn. IP NTWK Ring Number parameter for each source routing bridge. (Refer to “Editing Source Routing Global Parameters” later in this chapter for details on accessing this parameter.) Specify the same IP network ring ID for each Bay Networks source routing bridge that connects to the network.

• Enable IP encapsulation on the source routing bridges that connect to the IP

backbone. You reset the IP Encapsulation parameter to Enable for each source routing bridge. (Refer to “Editing Source Routing Global Parameters” later in this chapter for details on accessing this parameter.)

• Specify the IP Explorer list for each source routing interface that connects to

the IP backbone. The IP Explorer list deﬁnes the IP addresses that will receive explorer frames

from the bridge. These IP addresses are assigned to the token rings of remote users. (Refer to “Adding or Deleting an IP Address on the IP Explorer Address List” later in this chapter for details on the IP Explorer list.)

• Create directed explorer ﬁlters to reduce excess broadcast trafﬁc on the

network. (Refer to Conﬁguring Trafﬁc Filters and Protocol Prioritization for details on ﬁlters.)

Enabling Source Routing Services

This section describes how to enable the following services on an interface:

• Source routing

• Source routing spanning tree It assumes you have read Conﬁguring Routers and that you have

1. Opened a conﬁguration ﬁle

2. Speciﬁed router hardware if this is a local mode conﬁguration ﬁle

3. Selected the link or net module connector on which you are enabling source

routing, or conﬁgured a WAN circuit if this connector requires one

When you enable any of the source routing services, you are required to conﬁgure only a few parameters. The Conﬁguration Manager supplies default v alues for the remaining parameters. If you want to edit these default values, refer to “Enabling Source Routing Services on an Interface”

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Configuring Bridging Services

For each source routing parameter, this section pro vides information about default settings, valid parameter options, the parameter function, instructions for setting the parameter, and the Management Information Base (MIB) object ID.

The Technician Interface lets you modify parameters by issuing commands that specify the MIB object ID. This process is equivalent to modifying parameters using Site Manager. For more information about using the Technician Interface to access the MIB, refer to Using Technician Interface Software.

Caution: The Technician Interface does not verify that the value you enter for

a parameter is valid. Entering an invalid value can corrupt your conﬁguration.

Enabling Source Routing Services on an Interface

To enable source routing without spanning tree, use the following procedure.

1. Select Source Routing from the Select Protocols menu and click on OK.

The Select Protocols menu appears after you either select a link or net module connector, or ﬁnish conﬁguring a WAN circuit.

The Edit Source Routing Global Parameters window appears (Figure 2-14).

2. Specify the source routing bridge internal LAN ID and the source r outing

bridge ID, using the descriptions that follow as a guide.

set and commit

2-26

Note: Because source routing is global (that is, it runs across all Bridge

circuits), the Conﬁguration Manager only displays the Source Routing Global Parameters window the ﬁrst time you specify source routing for the bridge. If this window does not appear, source routing is already enabled on the bridge.

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Using Source Routing Bridge Services

Figure 2-14. Edit Source Routing Global Parameters Window

Parameter: SR Bridge Internal LAN ID

Default: 0x0

Range: 0x1 to 0xffe

Function: Speciﬁes this bridge’s internal LAN ID.

Instructions: Assign an internal LAN ID that is unique among all other internal LAN

IDs, group LAN IDs, and ring IDs in the network. You cannot use the value 0x0 that appears initially in the parameter box.

You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.4

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Configuring Bridging Services

Parameter: SR Bridge ID

Default: 0x0

Range: 0x1 to 0xf

Function: Speciﬁes this bridge’s bridge ID and identiﬁes the Bay Networks source

routing bridges in the network.

Instructions: Assign the same bridge ID to all Bay Networks source routing bridges in

the network (unless two bridges operate in parallel; see note below). The bridge ID must be unique among any other non-Bay Networks bridge IDs in the network.

You cannot use the value 0x0 that appears initially in the parameter box. You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.5

Note: If two Bay Networks source routing bridges operate in parallel, you

must assign a different SR bridge ID to one of the bridges. You must also specify the SR bridge ID in the Bridge Entry list for all other Bay Networks source routing bridges in the network. (See “Implementation Notes” for more information.)

2-28

3. When you have conﬁgured the required parameters in the Edit Source

Routing Global Parameters window, click on OK.

The SR Interface List window appears (Figure 2-15).

4. Specify the source routing ring number, using the description that follows

as a guide, and click on OK.

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Figure 2-15. SR Interface List Window

Using Source Routing Bridge Services

Parameter: Source Routing Ring Number

Default: 0x0

Range: 0x001 to 0xfff

Function: Identiﬁes the ring number (ring ID) of this source routing circuit.

Instructions: Assign a ring number (ring ID) to this source routing circuit that is unique

among any other ring IDs, group LAN IDs, or internal LAN IDs in the network.

You cannot use the value 0x0 that appears initially in the parameter box. You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.6

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Configuring Bridging Services

Enabling Source Routing Spanning Tree Service on an Interface

To enable source routing spanning tree on an interface, complete the following steps:

1. From the Select Protocols menu, select the Spanning Tree option that is

directly under the Source Routing option.

Note that the Conﬁguration Manager also selects the Source Routing option because this Spanning Tree protocol cannot run without source routing enabled.

If you have not yet enabled source routing on any circuit, the Edit Source Routing Global Parameters window appears (Figure 2-14). If you have enabled source routing on some other circuit, the SR Interface List window appears (Figure 2-15).

Refer to “Enabling Source Routing Services on an Interface” earlier in this chapter to conﬁgure the necessary source routing parameters.

2. After you conﬁgure the interface parameters and click on OK in the SR

Interface List window, the Source Route Spanning Tree Autoconﬁguration window appears (Figure 2-16).

2-30

Note: Because the spanning tree is global (that is, it runs across all source

routing circuits), the Conﬁguration Manager only displays the Source Route Spanning Tree Autoconﬁguration window the ﬁrst time you specify spanning tree for source routing. If you have previously speciﬁed spanning tree for source routing, this window will not appear.

Note: Although the parameters on this screen have the same names and

functions as for spanning sree service under bridging, they need to be set independently for spanning tree service under source routing.

3. Conﬁgure the Bridge Priority and Bridge MAC Address parameters,

using the descriptions that follow as a guide.

4. When you have conﬁgured the required parameters, click on OK.

A pop-up window prompts

Do you want to edit the Source Route Spanning Tree Interface Details?

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5. Click on Cancel to enable default spanning tree service and to display the

next protocol-speciﬁc window, or click on OK to edit the default values.

Refer to “Editing Source Routing Parameters” for instructions.

Figure 2-16. Source Route Spanning Tree Autoconﬁguration Window

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Parameter: Bridge Priority

Default: 128

Range: 0 to 65535

Function: Combined with the Bridge MAC Address parameter, assigns a 64-bit

bridge ID to the router. This parameter supplies the most signiﬁcant 16 bits of the bridge ID, while Bridge MAC Address supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowestnumber bridge ID. Thus, the lower the value of this parameter, the more likely that the router will be selected as the root bridge.

Instructions: Enter a decimal value from 0 to 65535.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.33

Parameter: Bridge MAC Address

Default: Defaults to a unique MAC address that the router automatically creates

based on the router’s backplane ID.

Options: Any valid, 48-bit MAC-level address

Function: Combined with the Bridge Priority parameter, assigns a 64-bit bridge ID

to the router. Bridge Priority supplies the most signiﬁcant 16 bits of the bridge ID, while this parameter supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowestnumber bridge ID. Thus, the lower the value of Bridge Priority, the more likely that the router will be selected as the root bridge. In the event of equal bridge priority values, the Bridge MAC Address value determines the bridge’s priority.

Instructions: Enter a 48-bit MAC address expressed as a 12-digit hexadecimal value.

You should set this parameter to the MAC address of one of the router’s spanning tree ports, preferably the one with the lowest priority.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.33

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Editing Source Routing Parameters

Once you conﬁgure a circuit to support source routing, you use the Conﬁguration Manager to edit the source routing parameters. This section provides information on how to access and edit these parameters.

Note: The instructions in this section assume that you have already conﬁgur ed

source r outing on the r outer. (Refer to “Enabling Source Routing Services” for details on conﬁguring source routing.)

You access all source routing parameters from the Conﬁguration Manager window (Figure 2-17). Refer to Using Site Manager Software for details on accessing this window.

Using Source Routing Bridge Services

Figure 2-17. Conﬁguration Manager Window

Editing Source Routing Global Parameters

To edit source routing global parameters:

1. Select Protocols➔Source Routing➔Global in the Conﬁguration Manager

window (Figure 2-17).

The Edit Source Routing Global Parameters window appears (Figure 2-18).

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Figure 2-18. Edit Source Routing Global Parameters Window

2. Edit the parameters, using the descriptions in the next section as a guide.

(Refer to Chapter 3 for details on editing the NetBIOS parameters.)

3. Click on OK to save your changes and exit the window.

Source Routing Global Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Edit Source Routing Global Parameters window (Figure 2-18). Refer to Chapter 3 for details on conﬁguring the NetBIOS parameters on this window.

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Parameter: Enable

Default: Enable

Using Source Routing Bridge Services

Options: Enable

Function: Enables or disables source routing on the entire router.

Instructions: Set to Disable if you want to disable source routing.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.2

Parameter: SR Bridge Internal LAN ID

Default: 0x0

Range: 0x1 to 0xffe

Function: Speciﬁes this bridge’s internal LAN ID.

Instructions: Assign an internal LAN ID that is unique among all other internal LAN

IDs, group LAN IDs, and ring IDs in the network. You cannot use the value 0x0 that appears initially in the parameter box.

You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.4

Parameter: SR Bridge ID

| Disable

Default: 0x0

Range: 0x1 to 0xf

Function: Speciﬁes this bridge’s bridge ID and identiﬁes the Bay Networks source

routing bridges in the network.

Instructions: Assign the same value to all Bay Networks source routing bridges in the

network (unless two bridges operate in parallel; see the following note). The SR bridge ID must be unique among any other non-Bay Networks bridge IDs in the network.

You cannot use the value 0x0 that appears initially in the parameter box. You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.5

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Note: If two Bay Networks source routing bridges operate in parallel, you

Parameter: SR Bridge Group LAN ID

Default: 0xfff

Range: 0x1 to 0xfff

Function: Speciﬁes this bridge’s group LAN ID. The bridge uses the group LAN ID

when transmitting speciﬁcally routed frames (SRFs) between Bay Networks bridges. Together with the other routing designators, the group LAN ID helps bridges manipulate the RIF.

Instructions: Assign the same group LAN ID to all Bay Networks source routing

bridges in the network. The group LAN ID must be unique among any other group LAN IDs, ring IDs, or internal LAN IDs in the network.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.6

Parameter: IP Encapsulation

Default: Disable

Options: Enable

Function: Enables IP encapsulation for those packets destined for an IP network.

Instructions: Enable this parameter if the bridge borders an IP network cloud and you

want to source-route frames across this IP network. If you enable this parameter, you must also conﬁgure the Conn. IP NTWK Ring number parameter for IP encapsulation to occur.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.7

Note: Refer to “Conﬁguring IP Encapsulation Support” earlier in this

chapter for details on IP encapsulation.

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Parameter: Conn. IP NTWK Ring number

Default: 0x0

Range: 0x1 to 0xffe

Function: Identiﬁes the ring ID of the IP network to which this bridge connects.

Instructions: Assign the same value to all Bay Networks source routing bridges that

border the IP network cloud. Make sure this value is unique among any other ring IDs, group LAN IDs, or internal LAN IDs in the network.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.8

Note: You cannot modify the Conn. IP NTWK Ring number parameter unless

you ﬁrst enable IP encapsulation. Refer to “Conﬁguring IP Encapsulation Support” earlier in this chapter for details on IP encapsulation.

Parameter: IP MTU Size (bytes)

Default: 4562

Range: 0 to 4562

Function: Speciﬁes the maximum MTU size for the IP network.

Instructions: Select a value that equals the smallest MTU size of any of the links in the

IP network. This allows the lar gest frame negotiation in the source routing exploration process to account for any link inside the IP cloud.

You can accept the default value 4562. However, if you have links in your IP network with smaller MTU sizes than the default value, the IP entity may fragment packets. For maximum performance, refer to your network conﬁguration and calculate this value based on actual MTU sizes.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.11

Editing Source Routing Interface Parameters

To edit a source routing interface:

1. Select Protocols➔Source Routing➔Interfaces in the Conﬁguration

Manager window (Figure 2-17).

The SR Interface List window appears (Figure 2-19).

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2-38

Figure 2-19. SR Interface List Window

2. Select the interface you want to edit.

3. Edit the parameters, using the descriptions in the next section as a guide.

Refer to Chapter 3 for descriptions of the NetBIOS parameters on this screen.

4. Click on Apply to save your changes.

5. Click on Done to exit the window. Site Manager returns you to the

Conﬁguration Manager window.

Note: When you reconﬁgure an interface in dynamic mode, source routing

restarts on that interface.

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Source Routing Interface Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the SR Interface List window (refer to Figure 2-19). (Refer to Chapter 3 for descriptions of the NetBIOS parameters on this screen.)

Parameter: Enable

Default: Enable

Options: Enable

Function: Enables or disables source routing over this circuit.

Instructions: Set this parameter to Enable to enable source routing over this circuit.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.2

Parameter: Max number of RDs

Default: 7

Range: 1 to 7

Function: Speciﬁes the maximum number of route descriptors allowed in incoming

explorer frames. Any explorer frames received that contain more route descriptors than speciﬁed here are dropped.

Instructions: Accept the default unless you want to limit the number of networks this

router can reach.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.5

| Disable

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Parameter: Source Routing Ring Number

Default: 0x0

Range: 0x001 to 0xfff

Function: Identiﬁes the ring number (ring ID) of this source routing circuit.

Instructions: Assign a ring number (ring ID) to this source routing circuit that is unique

among any other ring IDs, group LAN IDs, or internal LAN IDs in the network.

You cannot use the value 0x0 that appears initially in the parameter box. You must specify a value for this parameter that is within the given range.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.6

Parameter: Outbound STEs

Default: Accept

Options: Accept

Function: When set to Block, the bridge drops outbound STEs on this circuit. Use

this parameter to conﬁgure a static spanning tree for spanning tree explorer packets. This parameter has no effect if you conﬁgure this interface with the Source Routing Spanning Tree protocol.

Instructions: Set to Block only if you do not want the bridge to forward STEs on this

circuit.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.7

Note: Series 7 router software does not support dynamic source route

spanning tree. You must statically conﬁgure which ports should accept or block STE frames. Series 8 router softwar e does support dynamic source route spanning tree.

| Block

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Parameter: Inbound STEs

Default: Accept

Using Source Routing Bridge Services

Options: Accept

Function: Speciﬁes whether the bridge should drop single route explorer frames

received on this circuit. This option will not stop single route explorer frames from being transmitted on this circuit. This parameter has no effect if you conﬁgure this interface with the Source Routing Spanning Tree protocol.

Instructions: Set to Block only if you want spanning tree explorer packets to be

dropped by this circuit.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.8

Parameter: Frames with IP Ring

Default: Accept

Options: Accept

Function: Speciﬁes whether the bridge should block inbound explorer frames

received on this circuit that traversed the IP network via IP encapsulation.

Instructions: Set to Block only if you want to limit the route selection possibilities

using IP encapsulation.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.9

| Block

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Parameter: IP Address

Default: None

Options: Any valid IP address

Function: Shows the IP address of this interface. (If there is no IP address, this ﬁeld

displays 0.0.0.0.) You can use this parameter with the IP Encapsulation parameter to map

ring IDs to IP addresses.

Instructions: If you accept the IP address displayed, then the ring ID maps to that

address. If you want to change the ring ID mapping to the outgoing IP interface,

enter 0.0.0.0 at this ﬁeld.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.10.

Note: If you did not conﬁgure IP on this interface already, the system will

overwrite the value you entered for this parameter when you do conﬁgure IP.

Parameter: WAN Broadcast Address

Default: -1

Options: Any valid Frame Relay data link connection identiﬁer (DLCI) number

Function: Sets the DLCI number this interface uses when it sends broadcast frames

over Frame Relay.

Instructions: Specify a DLCI number.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.23

Note: You cannot modify the WAN Broadcast Address parameter unless you

ﬁrst conﬁgure source routing over Frame Relay, ATM, or SMDS.

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Parameter: Encapsulation Format

Default: Proprietary

Using Source Routing Bridge Services

Options: Proprietary

Function: Indicates Bay Networks proprietary encapsulation format or standard

encapsulation format.

Instructions: If you want to run source routing over a Frame Relay network, follow

these instructions: – If your router, running software Version 8 or higher, communicates

with a third-party router that supports RFC 1490, and you conﬁgured both routers to run source routing over Frame Relay, select Standard for RFC 1490 standard Frame Relay encapsulation.

– If your router, running software Version 8 or higher, communicates

with a Version 5 Bay Networks router, and you conﬁgured both routers to run source routing over Frame Relay, accept the default, Proprietary.

– If your Version 8 router communicates with a Version 7 Bay

Networks router, and you conﬁgured both routers to run source routing over Frame Relay, select Standard.

– If your router, running software Version 8 or higher, communicates

with another Version 8 router, and you conﬁgured both routers to run source routing over Frame Relay, you can select either Proprietary or Standard; however, you must set the same encapsulation format for both routers.

| Standard

If you want to bridge between source routing Token Ring and FDDI endstations, refer to the following instructions:

– If your router, running software Version 8 or higher, connects Token

Ring endstations to FDDI endstations, select Standard for standard native encapsulation.

– If your router, running software Version 8 or higher, communicates

with a third-party router via an FDDI network, and each router connects to a Token Ring network, select Standard.

– If your router communicates with a Version 5 or Version 7 router via

an FDDI network, and each router connects to a Token Ring network, accept the default, Proprietary.

– If your router, running software Version 8 or higher, communicates

with another router running Version 8 or higher via an FDDI network,

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you can select either Proprietary or Standard; however, you must set the same encapsulation format for both routers.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.24

Adding or Deleting a Bridge ID on the Bridge Entry List

You specify a bridge ID on the Bridge Entry list if you want to conﬁgure two or more Bay Networks source routing bridges in parallel. (Refer to “Assigning Bridge IDs, Internal LAN IDs, and Group LAN IDs” in this chapter for more information.) The following sections describe how to add and delete a bridge ID in the Bridge Entry list.

Adding a Bridge Entry to the Bridge Entry List

To add a bridge ID:

1. Select Protocols➔Source Routing➔Bridge Entry in the Conﬁguration

Manager window (refer to Figure 2-17).

The Source Routing Bridge IDs window appears, which lists the bridge IDs currently conﬁgured on the network (Figure 2-20).

2-44

Figure 2-20. Source Routing Bridge IDs Window

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Using Source Routing Bridge Services

2. Click on Add.

The Add Bridge ID window appears (Figure 2-21).

Figure 2-21. Add Bridge ID Window

Enter the new bridge ID in the New Source Routing Bridge ID ﬁeld,

using the description in the next section as a guide.

4. Click on Add SR BR ID. Site Manager r etur ns y ou to the Sour ce Routing

Bridge IDs window.

The bridge ID you conﬁgured now appears in the Bridge Entry list.

5. Click on Done to exit the window. Site Manager returns you to the

Conﬁguration Manager window.

Source Routing Bridge ID Parameter Description

Use this parameter description as a guide when you conﬁgure the parameter in the Add Bridge ID window (refer to Figure 2-21).

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Parameter: New Source Routing Bridge ID

Default: None

Range: 1 to 15

Function: Speciﬁes the other active bridge IDs that exist on the network. This

parameter is only necessary if you have parallel source routing bridges conﬁgured on your network.

Instructions: Enter the bridge ID assigned to the parallel bridge on your network. Refer

to “Assigning Bridge IDs, Internal LAN IDs, and Group LAN IDs” for details on parallel source routing bridges.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.3.1.1

Deleting a Bridge Entry from the Bridge Entry List

To delete a bridge ID:

1. Select Protocols➔Source Routing➔Bridge Entry in the Conﬁguration

Manager window (refer to Figure 2-17).

The Source Routing Bridge IDs window appears, which lists the other bridge IDs currently conﬁgured on the network (refer to Figure 2-20).

2. Select a bridge ID from the list.

3. Click on Delete.

The bridge ID you deleted no longer appears in the Bridge Entry list.

4. Click on Done to exit the window. Site Manager returns you to the

Conﬁguration Manager window.

Adding or Deleting an IP Address on the IP Explorer Address List

You specify an IP address on the IP Explorer Address list if you want to source route across an IP network. The following sections describe ho w to add and delete an IP address in the IP Explorer Address list.

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Adding an IP Explorer Address to the IP Explorer Address List

To add an IP explorer address:

1. Select Protocols➔Source Routing➔Explorer Entry in the Conﬁguration

Manager window (refer to Figure 2-17).

The Source Routing Bridge IP Explorer Addresses window appears (Figure 2-22), which lists the deﬁned IP explorer addresses.

Figure 2-22. Source Routing Bridge IP Explorer Addresses Window

Click on Add.

The Add Source Routing Explorer IP Address window appears (Figure 2-23).

Figure 2-23. Add Source Routing Explorer IP Address Window

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Enter the new IP address in the New SR Bridge Explorer IP address ﬁeld,

using the description in the next section as a guide.

4. Click on Add SR BR EXP.

Site Manager returns you to the Source Routing Bridge IP Explorer Addresses window .

The IP address you conﬁgured now appears in the list.

5. Click on Done to exit the window.

Site Manager returns you to the Conﬁguration Manager window.

IP Explorer Address Parameter Description

Use this parameter description as a guide when you conﬁgure the parameter in the Add Source Routing Explorer IP Address window (refer to Figure 2-23).

Parameter: New SR Bridge Explorer IP address

Default: None

Options: Any valid IP address.

Function: Speciﬁes a destination IP address that this bridge can use to source-route

packets across an IP network.

Instructions: Enter a valid destination IP address.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.4.1.1

Deleting an IP Explorer Address

To delete an IP address from the IP Explorer Address list:

1. Select Protocols➔Source Routing➔Explorer Entry in the Conﬁguration

Manager window (refer to Figure 2-17).

The Source Routing Bridge IP Explorer Addresses window appears (refer to Figure 2-22), which lists the deﬁned IP explorer addresses.

2. Select an IP address from the list.

3. Click on Delete.

The IP address you deleted no longer appears in the IP Explorer Address list.

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4. Click on Done to exit the window.

Site Manager returns you to the Conﬁguration Manager window.

Editing Source Route Spanning Tree Global Parameters

To edit the source route spanning tree global parameters:

1. Select Protocols➔Source Routing➔Spanning T ree➔Global in the

Conﬁguration Manager window (refer to Figure 2-17).

The Edit Source Route Spanning Tree Global Parameters window appears (Figure 2-24).

Figure 2-24. Edit Source Route Spanning Tree Global Parameters Window

Edit the parameters, using the descriptions in the next section as a guide.

3. Click on OK to save your changes and exit the window.

Site Manager returns you to the Conﬁguration Manager window.

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Source Route Spanning Tree Global Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Edit Source Route Spanning Tree Global Parameters window (refer to Figure 2-24).

Parameter: Spanning Tree Enable

Default: Enable

Options: Enable

Function: Enables or disables spanning tree on the entire router.

Instructions: Set to Disable if you want to disable spanning tree for the entire router, or

to Enable if you want to re-enable spanning tree for the entire router.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.30

Parameter: Spanning Tree Protocol Version

Default: IEEE8021D

Options: IEEE8021D

Function: Speciﬁes the version of the spanning tree protocol that the router is

running.

Instructions: Accept the default, IEEE8021D, or select one of the other options.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.32

| Disable

| Unknown | DECLB108

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Parameter: Bridge Priority

Default: 128

Range: 0 to 65535

Function: Combined with the Bridge MAC Address parameter, assigns a 64-bit

bridge ID to the router. This parameter supplies the most signiﬁcant 16 bits of the bridge ID, while Bridge MAC Address supplies the remaining (least signiﬁcant) 48 bits.

Instructions: Enter a decimal value from 0 to 65535.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.33

Parameter: Bridge MAC Address

Default: Defaults to a unique MAC address that the router automatically creates

based on the router’s backplane ID.

Options: Any valid, 48-bit MAC-level address

Function: Combined with the Bridge Priority parameter, assigns a 64-bit bridge ID

to the router. Bridge Priority supplies the most signiﬁcant 16 bits of the bridge ID, while this parameter supplies the remaining (least signiﬁcant) 48 bits.

The spanning tree uses the bridge ID to select the root bridge. In selecting the root bridge, the spanning tree chooses the bridge with the lowestnumber bridge ID. Thus, the lower the value of Bridge Priority, the more likely that the router will be selected as the root bridge. In the event of equal bridge priority values, the Bridge MAC Address value determines the bridge’s priority.

Instructions: Enter a 48-bit MAC address expressed as a 12-digit hexadecimal value.

You should set this parameter to the MAC address of one of the router’s spanning tree ports, preferably the one with the lowest priority.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.33

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Caution: We recommend that you not change the following three spanning

tree parameters (Max Age, Hello Time, and Forward Delay) unless absolutely necessary. However, if you do change them, you must follow these guidelines.

2 x (Forward Delay – 1 Second) ≥ Max Age Max Age ≥ 2 x (Hello Time + 1 Second)

Note: If the values for Max Age, Hello Time, and Forward Delay are not the

same for each bridge in your network, the root bridge parameters rule the entire topology.

Parameter: Max Age

Default: 20 seconds (expressed in hundredths of a second: 2000)

Range: 6 to 40 seconds

Function: Speciﬁes the maximum number of seconds that the router considers

protocol information (BPDUs) valid. After this speciﬁed amount of time, the router times out and discards the information.

We recommend that you accept the default value; however, if you change it, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or specify a new value. Make sure to

express any new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.43

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Parameter: Hello Time

Default: 2 seconds (expressed in hundredths of a second: 200)

Range: 1 to 10 seconds

Function: Speciﬁes the interval in seconds between BPDUs transmitted by the

bridge. BPDUs are periodic transmissions exchanged between bridges in the network to convey conﬁguration and topology change data.

We recommend that you accept the default value; however, if you change it, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or enter a new value. Make sure you enter

the new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.44

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Parameter: Forward Delay

Default: 15 seconds (expressed in hundredths of a second: 1500)

Range: 4 to 30 seconds

Function: Speciﬁes the time in seconds that a circuit spends in the listening and

learning states. If you set this parameter to the minimum value, the spanning tree converges at its fastest rate.

As the spanning tree algorithm operates, it eventually places all circuits in either a forwarding (enabled) or blocking (disabled) state. In response to network topology changes, the spanning tree algorithm may change the state of speciﬁc circuits. To prevent network looping caused by sudden state changes, the spanning tree algorithm does not transition circuits directly from the blocking to the forwarding state. Rather, it places them in two intermediate states: listening and learning.

In the learning state, the circuit receives both network-generated BPDUs, and endstation-generated trafﬁc that is subjected to the learning process but is not relayed. When the forward delay timer expires, the spanning tree algorithm places the circuit in the forwarding state.

We recommend that you accept the default, 15 seconds; however, if you change the value, you must follow the guidelines listed previously in this section.

Instructions: Either accept the default value or enter a new value. Make sure you enter

the new value in hundredths of a second.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.1.45

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Editing Source Route Spanning Tree Interface Parameters

To edit the source route spanning tree interface parameters:

1. Select Protocols➔Source Routing➔Spanning T ree➔Interfaces in the

Conﬁguration Manager window (refer to Figure 2-17).

The Source Route Spanning Tree Interface List window appears (Figure 2-25).

Figure 2-25. Source Route Spanning Tree Interface List Window

Edit the parameters, using the descriptions in the next section as a guide.

3. Click on OK to save your changes.

4. Click on Done to exit the window.

Site Manager returns you to the Conﬁguration Manager window.

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Source Route Spanning Tree Interface Parameter Descriptions

Use these parameter descriptions as a guide when you conﬁgure the parameters in the Source Route Spanning Tree Interface List window (refer to Figure 2-25).

Parameter: Enable

Default: If you added spanning tree using either the Quick-Start procedure or the

conﬁguring-circuits procedure, this parameter defaults to Enable. If you previously used this parameter to disable spanning tree on this circuit, the parameter defaults to Disable.

Options: Enable

Function: Toggles spanning tree on and off for this circuit only.

This parameter does not allow you to add spanning tree to this circuit. To add the spanning tree to this circuit, you must use the conﬁguring-circuits procedure. For instructions, see Conﬁguring Routers.

Instructions: Set this parameter to either Enable or Disable.

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.25

Parameter: Path Cost

Default: 1

Range: 1 to 65535

Function: When this port is the root port, the path cost is the contribution of the path

through this port to the total cost of the path to the root for this bridge. When this port is not the root port, the router adds the path cost to the designated cost for the root port and uses it as the value of the root path cost offered in all conﬁguration BPDUs transmitted by the bridge.

To determine the path cost, use this formula: Interface Path Cost = 1000/Attached LAN speed in Mb/s

| Disable

Instructions: Enter a path cost value for this interface in the Path Cost box. For

example, enter 100 if the attached LAN is Ethernet (1000/10 = 100).

MIB Object ID: 1.3.6.1.4.1.18.3.5.1.1.2.2.1.28

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