Example: Setting Metrics for Routes Forwarded on the Basis of Communities

This example shows how to set metrics for routes forwarded on the basis of communities.

Requirements

This example uses the following software and hardware components:

Overview

Consider the network structure shown in Figure 5. In this network, you can configure router Albany to set metrics for routes that it forwards to router Boston on the basis of the communities to which the routes belong. You can create community lists and filter the routes with a route map that matches on the community list.

Figure 5: Community Lists

Community Lists

Configuration

Step-by-Step Procedure

The following example demonstrates about configuring router Albany to set metrics for routes that it forwards to router Boston on the basis of the communities.

To configure router Albany to set metrics for routes:

  1. Configure the BGP routing process.
    host1(config)#router bgp 293
  2. Add entries to the BGP neighbor table.
    host1(config-router)#neighbor 10.5.5.2 remote-as 32 host1(config-router)#neighbor 10.2.2.1 remote-as 451 host1(config-router)#neighbor 10.2.2.4 remote-as 17
  3. Apply a route map to incoming or outgoing routes.
    host1(config-router)#neighbor 10.2.2.4 route-map commtrc out host1(config-router)#exit
  4. Specify route map 1 and configure route map match and set clauses.
    host1(config)#route-map commtrc permit 1 host1(config-route-map)#match community 1 host1(config-route-map)#set metric 20 host1(config-route-map)#exit
  5. Specify route map 2 and configure route map match and set clauses.
    host1(config)#route-map commtrc permit 2 host1(config-route-map)#match community 2 host1(config-route-map)#set metric 75 host1(config-route-map)#exit
  6. Specify route map 3 and configure route map match and set clauses.
    host1(config)#route-map commtrc permit 3 host1(config-route-map)#match community 3 host1(config-route-map)#set metric 85 host1(config-route-map)#exit
  7. Create community lists for BGP and control access to it.
    host1(config)#ip community-list 1 permit 25 host1(config)#ip community-list 2 permit 62 host1(config)#ip community-list 3 permit internet

Results

Community list 1 comprises routes with a community of 25; their metric is set to 20. Community list 2 comprises routes with a community of 62; their metric is set to 75. Community 3 catches all remaining routes by matching the Internet community; their metric is set to 85.

Related Documentation