8.8.2 Configuring route summarization and summarized route advertisement

Configure summarization of directly connected routes as summarization source routes. Also, configure the switch to re-advertise the summarized and directly connected routes by BGP4 without re-advertising directly connected routes that became summarization source routes.

Figure 8-18: Configuration in which summary routes are advertised by BGP4

Points to note

To generate a summarized route, use the ip summary-address command. Use the redistribute summary command to configure BGP4 to advertise the summarized route.

Command examples

1. (config)# ip summary-address 172.16.0.0 255.255.0.0 summary-only

   Configures the switch to generate the summarized route 172.16.0.0/16. By specifying summary-only, you suppress re-advertisement of the directly connected route 172.16.1.0/24 serving as the summarization source.

2. (config)# router bgp 100

   (config-router)# neighbor 192.168.100.2 remote-as 200

   Establishes a BGP4 connection with neighboring router 192.168.100.2.

3. (config-router)# redistribute summary

   Uses BGP4 to re-advertise the summarized route.

4. (config-router)# redistribute connected

   Uses BGP4 to re-advertise the directly connected route.