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Cisco Systems BC-23 Setting the Bridge Priority, Setting an Interface Priority, Assigning Path Costs, Adjusting BPDU Intervals

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Configuring Transparent Bridging

Transparent and SRT Bridging Configuration Task List

BC-53

Cisco IOS Bridging and IBM Networking Configuration Guide

Note Only network administrators with a good understanding of how bridges and the

Spanning-Tree Protocol work should make adjustments to spanning-tree parameters.

Poorly planned adjustments to these parameters can have a negative impact on

performance. A good source on bridging is the IEEE 802.1d specification; see the

“References and Recommended Reading” appendix in the Cisco IOS Configuration

Fundamentals Command Reference for other references.

Setting the Bridge Priority

You can globally configure the priority of an individual bridge when two bridges tie for position as the

root bridge, or you can configure the likelihood that a bridge will be selected as the root bridge. This

priority is determined by default; however, you can change it. To set the bridge priority, use the following

command in global configuration mode:

Setting an Interface Priority

You can set a priority for an interface. When two bridges tie for position as the root bridge, you configure

an interface priority to break the tie. The bridge with the lowest interface value is elected. To set an

interface priority, use the following command in interface configuration mode:

Assigning Path Costs

Each interface has a path cost associated with it. By convention, the path cost is 1000/data rate of the

attached LAN, in Mbps. You can set different path costs. Refer to the entry for this command in the Cisco

IOS Bridging and IBM Networking Command Reference, Volume I for the various media defaults. To

assign path costs, use the following command in interface configuration mode:

Adjusting BPDU Intervals

You can adjust BPDU intervals as described in the following sections:

•Adjusting the Interval between Hello BPDUs

•Defining the Forward Delay Interval

•Defining the Maximum Idle Interval

Command Purpose

bridge bridge-group priority number Sets the bridge priority.

Command Purpose

bridge-group bridge-group priority number Establishes a priority for a specified interface.

Command Purpose

bridge-group bridge-group path-cost cost Sets a path cost different from the defaults.

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