This section describes how to configure a source route bridge to operate in a token ring or Fiber Distributed Data Interface (FDDI) environment. (NETBuilder II bridge/routers only support an FDDI environment.) In this section, a network with multiple rings or other network segments is called an extended network. For information on how to configure a source route bridge to operate in a wide area networking environment, see "Configure Source Route Bridging over a Wide Area Network" later in this chapter.

Source route bridging is supported on token ring, FDDI, Point-to-Point Protocol (PPP), Frame Relay, Asynchronous Transfer Mode (ATM), Asynchronous Transfer Mode data exchange interface (ATM DXI), X.25, Switched Multimegabit Data Service (SMDS), and Integrated Services Digital Network (ISDN). Also, configuring source route bridging can affect IBM-related services such as SDLC or DLSw. For more information, see "Configuring LLC2 with Other Services" in the Configuring the LLC2 Data Link Interface chapter.

Prerequisites

This section assumes that you have logged on to the system with Network Manager privilege and set up the ports and paths of your source route bridge according to the Configuring Basic Ports and Paths chapter and the Configuring Advanced Ports and Paths chapter.

Before setting up a source route bridge, you need to examine your network topology and generate the following:

• A unique number for each ring in an extended network. For example, in the topology shown in Figure 35, the four rings have been assigned hexadecimal ring numbers (RNs) 0x20, 0x30, 0x40, and 0x50. In Figure 36, the two rings have been assigned hexadecimal RNs 0x20 and 0x40. In addition, the serial interfaces have been assigned the hexadecimal RNs 0x30 and 0x50.

• A unique number for each bridge in a set of parallel bridges. For example, in the topology shown in Figure 35, parallel bridges B and E have been assigned the hexadecimal bridge numbers (BNs) 0x4 and 0x5. (When more than one bridge interconnects the same networks, the bridges are called parallel bridges.)

Figure 35 Sample FDDI or Token Ring Topology Using NETBuilder II Bridge/Router

Figure 36 Sample Token Ring Topology Using SuperStack II Bridge/Routers

Procedure

Figure 37 shows a sample token ring topology, which you can see while performing this procedure.

Figure 37 Source Route Bridging Sample Topology

To configure a source route bridge, follow these steps:

1 .   If you are configuring a source route bridge to operate in an FDDI environment, skip this step and go to step 3. If you are configuring a source route bridge to operate in a token ring environment, you may need to set the ring speed of each path.

The default ring speed is 4 Mb. If your source route bridge is a NETBuilder II, you need to perform this step only if your network is composed of 16 Mb rings. If your source route bridge is a model 32x or 52x SuperStack II NETBuilder bridge/router, the ring speed is automatically detected upon startup. You need to perform this step only if your bridge is connected to an intelligent hub and your network is composed of 16 Mb rings.

For example, to set the ring speed of path 1 of BR1 and BR2 (as shown in Figure 37) to 16 Mb, enter the following command on both bridges:

SETDefault !1 -PATH BAud = 16000

A message similar to the following appears:

Note: You must Enable -PATH CONTrol for this Path parameter to take effect.

2 .   Enable the paths you set the ring speed for in step 1 using:

SETDefault !<path> -PATH CONTrol = Enabled

A message similar to the following appears:

Thu Jan 1 09:09:14 1995 Path 1 available

At this point, connect the DB9 end of the token ring cable that leads from the 16 Mb ring to the token ring interface on your bridge/router.

It will take a minute or two for path 1 to start operating. When path 1 is operational, the system responds with a display similar to the following:

Thu Jan 1 09:12:36 1995 Path 1 UP

3 .   Assign each bridge port on your network the ring number of the network it accesses.

If you are setting up a pure router to forward packets to end systems on an extended network, skip this step.

To assign a ring number, use:

SETDefault !<port> -SR RingNumber = <number> (1-4095) | 0x<number> (1-FFF)]

For example, to assign the hexadecimal ring number 0xA to BR1 path 1, as shown in Figure 37, enter:

SETDefault !1 -SR RingNumber = 0xA

To assign the equivalent decimal ring number to BR1 path 1, enter:

SETDefault !1 -SR RingNumber = 10

A serial line running PPP, Frame Relay, ATM DXI, SMDS, or X.25 is treated as a virtual ring.

4 .   Assign a different bridge number to each bridge in a set of parallel bridges using:

SETDefault !<port> -SR BridgeNumber = <number> (0-15) | 0x<number> (0-F)

If your network is not composed of parallel bridges, you do not need to assign a unique bridge number to each bridge. You can use the default setting of 3.

To assign the hexadecimal bridge number 0xC to a bridge, enter:

SETDefault -SR BridgeNumber = 0xC

To assign the equivalent decimal bridge number to a bridge, enter:

SETDefault -SR BridgeNumber = 12

5 .   Enable global bridging on each bridge.

For example, enable bridging on BR1 and BR2 by entering the following command on each bridge:

SETDefault -BRidge CONTrol = Bridge

Source route bridging is enabled by default on all ports (the default setting of the -SR SrcRouBridge parameter is SrcRouBridge) and source route bridging should begin to operate after you assign a ring number and enable global bridging.

6 .   If you do not want to operate in source route transparent (SRT) mode, disable per-port transparent bridging using:

SETDefault !<port> -BRidge TransparentBridge = NoTransparentBRidge

Transparent bridging is not supported on models 32x and 52x SuperStack II NETBuilder bridge/routers. You do not need to perform this step for this model.

After you complete this procedure, go to "Verifying the Configuration" later in this chapter.

You can configure your source route bridge to forward packets over the following types of wide area networks:

• PPP

• Frame Relay

• Asynchronous Transfer Mode (ATM)

• Asynchronous Transfer Mode Data Exchange Interface (ATM DXI)

• X.25

• SMDS

For complete information on configuring PPP, see the Configuring Wide Area Networking Using PPP chapter.

Source Route Bridging over Frame Relay, ATM, ATM DXI, and X.25

Source route bridging over Frame Relay, ATM, ATM DXI, and X.25 is supported over fully meshed, partially meshed, and nonmeshed topologies. If you plan to source route bridge over a partially meshed or nonmeshed topology, you must create a virtual port for each remote network that is attached to a Frame Relay, ATM DXI, or X.25 cloud. For complete information on configuring source route bridging over Frame Relay, ATM, or ATM DXI, including a discussion of fully meshed, partially meshed, or nonmeshed topologies and virtual ports, see the Configuring Wide Area Networking Using Frame Relay chapter, the Configuring Internetworking Using ATM chapter, and the Configuring Wide Area Networking Using the ATM DXI chapter. For complete information on configuring source route bridging over X.25, including a discussion of fully meshed, partially meshed, or nonmeshed topologies and virtual ports, see the Configuring Wide Area Networking Using X.25 chapter. For information on the number of virtual ports supported per platform, see Table 11 in the Configuring Advanced Ports and Paths chapter.

When creating virtual ports over a heavily trafficked partially meshed or nonmeshed topology, 3Com recommends that each source route bridge on the Frame Relay, ATM, ATM DXI, or X.25 network have a permanent virtual circuit for the proper operation of the Spanning Tree Protocol. Figure 38 shows a network composed of two NETBuilder II bridges and a model 327 SuperStack II bridge connected by virtual ports. The interconnection of the three source route bridges causes a potential loop. The Spanning Tree Protocol can prevent this loop by blocking a route as shown in Figure 38.

Figure 38 Source Route Bridging Over Frame Relay or X.25 in a Nonmeshed Topology with a Potential Loop

Source Route Bridging over SMDS

Source route bridging over SMDS is supported over fully meshed and hierarchical partially meshed topologies (where virtual ports are configured to attach to distinct groups of fully meshed devices). To configure source route bridging over SMDS, see the Configuring Wide Area Networking Using SMDS chapter.

Source Route Bridging over ISDN

For information on wide area networking using Integrated Services Digital Network (ISDN), see the Configuring Wide Area Networking Using ISDN chapter.