Cabletron Systems 9032578-05 manual Ebgp Aggregation Example, AS-64900, AS-64901

Chapter 12: BGP Configuration Guide

Routers SSR4 and SSR6 inform router C1 about network 172.16.200.0/24 through External BGP (EBGP). Router SSR6 announced the route with a MED of 10, whereas router SSR4 announces the route with a MED of 20. Of the two EBGP routes, router C1 chooses the one with a smaller MED. Thus router C1 prefers the route from router SSR6, which has a MED of 10.

Router SSR4 has the following CLI configuration:

bgp create peer-group pg752to751 type external autonomous-system 64751 bgp add peer-host 10.200.12.15 group pg752to751

#

#Set the MED to be announced to peer group pg752to751

bgp set peer-group pg752to751 metric-out 20

Router SSR6 has the following CLI configuration:

bgp create peer-group pg752to751 type external autonomous-system 64751 bgp add peer-host 10.200.12.15 group pg752to751

bgp set peer-group pg752to751 metric-out 10

EBGP Aggregation Example

Figure 16 shows a simple EBGP configuration in which one peer is exporting an aggregated route to its upstream peer and restricting the advertisement of contributing routes to the same peer. The aggregated route is 212.19.192.0/19.

AS-64900

212.19.199.62/24

212.19.198.1/24

212.19.192.2/24

SSR8

AS-64901

194.109.86.6194.109.86.5

Legend:

SSR9

Physical Link

Peering Relationship

Figure 16. Sample BGP Configuration (Route Aggregation)

156 SmartSwitch Router User Reference Manual