Cisco Systems BC-23 Ethernet Bridging Example

Configuring Transparent Bridging

Transparent and SRT Bridging Configuration Examples

BC-71

Cisco IOS Bridging and IBM Networking Configuration Guide

If the other side of the FDDI ring were an FDDI interface running in encapsulation mode rather than in

transparent mode, the following additional configuration commands would be needed:

interface fddi 0

fddi encapsulate

Ethernet Bridging Example

In the following example, two buildings have networks that must be connected via a T1 link. For the

most part, the systems in each building use either IP or DECnet, and therefore, should be routed. There

are some systems in each building that must communicate, but they can use only a proprietary protocol.

The example places two Ethernets in each building. One of the Ethernets is attached to the hosts that use

a proprietary protocol, and the other is used to attach to the rest of the building network running IP and

DECnet. The Ethernet attached to the hosts using a proprietary protocol is enabled for bridging to the

serial line and to the other building.

Figure 16 shows an example configuration. The interfaces marked with an asterisk (*) are configured as

part of spanning tree 1. The routers are configured to route IP and DECnet. This configuration permits

hosts on any Ethernet to communicate with hosts on any other Ethernet using IP or DECnet. In addition,

hosts on Ethernet 1 in either building can communicate using protocols not supported for routing.

Figure 16 Ethernet Bridging Configuration Example

Router/Bridge in Building 1

The configuration file for the router in Building 1 would be as follows. Note that no bridging takes place

over Ethernet 0. Both IP and DECnet routing are enabled on all interfaces.

decnet address 3.34

interface ethernet 0

ip address 128.88.1.6 255.255.255.0

decnet cost 10

!

interface serial 0

ip address 128.88.2.1 255.255.255.0

bridge-group 1

decnet cost 10

!

interface ethernet 1

ip address 128.88.3.1 255.255.255.0

bridge-group 1

decnet cost 10

!

bridge 1 protocol dec

S1094a

Router in

Building 1

E0

E1

Router in

Building 2

E0

E1

S0 S0

T1 Link

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Contents

Main Configuring Transparent Bridging Technology Overview Transparent and SRT Bridging Transparent Bridging Features Integrated Routing and Bridging Bridge-Group Virtual Interface Page Other Considerations SRT Bridging Features Transparent and SRT Bridging Configuration Task List Configuring Transparent Bridging and SRT Bridging Assigning a Bridge Group Number and Defining the Spanning-Tree Protocol Assigning Each Network Interface to a Bridge Group Choosing the OUI for Ethernet Type II Frames Transparently Bridged VLANs for ISL Page Routing between ISL VLANs Page Configuring a Subscriber Bridge Group Configuring Transparent Bridging over WANs Configuring Fast-Switched Transparent Bridging over ATM Configuring Transparent Bridging over DDR Configuring Transparent Bridging over Frame Relay Configuring Transparent Bridging over Multiprotocol LAPB Configuring Transparent Bridging over SMDS Configuring Transparent Bridging over X.25 Configuring Concurrent Routing and Bridging Configuring Integrated Routing and Bridging Assigning a Bridge Group Number and Defining the Spanning-Tree Protocol Configuring Interfaces Enabling Integrated Routing and Bridging Configuring the Bridge-Group Virtual Interface Configuring Protocols for Routing or Bridging Configuring Transparent Bridging Options Disabling IP Routing Enabling Autonomous Bridging Configuring LAT Compression Establishing Multiple Spanning-Tree Domains Preventing the Forwarding of Dynamically Determined Stations Forwarding Multicast Addresses Configuring Bridge Table Aging Time Filtering Transparently Bridged Packets Setting Filters at the MAC Layer Filtering by Specific MAC Address Page Page Page Filtering LAT Service Announcements Specifying Deny or Permit Conditions for LAT Group Codes on Output Adjusting Spanning-Tree Parameters Setting the Bridge Priority Setting an Interface Priority Assigning Path Costs Adjusting BPDU Intervals Disabling the Spanning Tree on an Interface Configuring Transparent and IRB Bridging on a PA-12E/2FE Ethernet Switch Configuring the PA-12E/2FE Port Adapter Monitoring and Maintaining the PA-12E/2FE Port Adapter Configuring Bridge Groups Using the 12E/2FE VLAN Configuration WebTool Page Tuning the Transparently Bridged Network Configuring Circuit Groups Configuring Constrained Multicast Flooding Monitoring and Maintaining the Transparent Bridge Network Transparent and SRT Bridging Configuration Examples Basic Bridging Example BC-64 The configuration file for the router in Figure 12 is as follows: Concurrent Routing and Bridging Example BC-65 Basic Integrated Routing and Bridging Example Figure 13 Basic IP Routing using Integrated Routing and Bridging The following example shows the relevant portions of the configuration for the router in Figure 13: BC-66 Complex Integrated Routing and Bridging Example Figure 14 Complex Integrated Routing and Bridging Example The following example shows the relevant portions of the configuration for the router: BC-67 Integrated Routing and Bridging with Multiple Bridge Groups Example Figure 15 Integrated Routing and Bridging with Multiple Bridge Groups The following example shows the relevant portions of the configuration for the router in Figure 15: Transparently Bridged VLANs Configuration Example BC-68 Router One Router Two BC-69 Router Three BC-70 Routing between VLANs Configuration Example Ethernet-to-FDDI Transparent Bridging Example Ethernet Bridging Example SRT Bridging Example BC-73 Configuration for the New York City Router Configuration for the Thule, Greenland Router Multicast or Broadcast Packets Bridging Example Figure 18 Network Demonstrating Output Address List Filtering BC-74 The correct access list would be as follows: X.25 Transparent Bridging Example Figure 19 X.25 Bridging Examples Following are the configuration commands for each of the bridges depicted in Figure19: X.25 Bridge 2 Bridge 1 Bridge 3 BC-75 Frame Relay Transparent Bridging Examples Figure 20 illustrates three bridges connected to each other through a Frame Relay network. Figure 20 Frame Relay Bridging Example Bridging in a Frame Relay Network with No Multicasts Bridge 2 Bridge 1 Bridge 3 Transparent Bridging over Multiprotocol LAPB Example BC-77 Fast-Switched Transparent Bridging over ATM Example (Cisco 7000) The following configuration example enables fast-switched transparent bridging over ATM: Transparent Bridging over DDR Examples Fast-Switched Transparent Bridging over SMDS Example Complex Transparent Bridging Network Topology Example Page Page Page BC-82 Fast Ethernet Subscriber Port, Frame Relay Trunk Example ATM Subscriber Ports, ATM Trunk Example The following example uses ATM subinterfaces as the subscriber ports and the ATM as the trunk: BC-83 Configuration of Transparent Bridging for PA-12E/2FE Port Adapter Example BC-84 Configuration of IRB for PA-12E/2FE Port Adapter Example