Enterasys Networks X-PeditionTM BGP Aggregate Route Examples, Configuring BGP Confederations

Configuring BGP Route Maps

XSR(config-router)#neighbor 192.168.57.69 filter-list 3 out

XSR(config-router)#neighbor 192.168.57.69 filter-list 2 in

XSR(config-router)#exit

XSR(config)#ip as-path access-list 1 permit _102_

XSR(config)#ip as-path access-list 2 permit _200$

XSR(config)#ip as-path access-list 2 permit ^100$

XSR(config)#ip as-path access-list 3 deny _440$

XSR(config)#ip as-path access-list 3 permit .*

BGP Aggregate Route Examples

The following examples describe how to use aggregate routes in BGP either by redistributing an aggregate route into BGP or by using the conditional aggregate routing feature.

In the next example, redistribute aggregate route 192.*.*.*:

XSR(config)#ip route 192.0.0.0 255.0.0.0 null 0

XSR(config)#router bgp 57

XSR(config-router)#redistribute static

In the following example, add an aggregate entry in the BGP routing table when at least one route falls into the specified range. The XSR will advertise this route as originating from your AS and has the atomic aggregate attribute set to indicate data may be lost. (By default, atomic aggregate is set unless you use the as-setkeyword in the aggregate-addresscommand.)

XSR(config)#router bgp 57

XSR(config-router)#aggregate-address 192.0.0.0 255.0.0.0

Next, you add an aggregate entry using similar rules as in the previous example, but the path advertised for this route will be an AS_SET consisting of all elements within all paths being summarized:

XSR(config)#router bgp 57

XSR(config-router)#aggregate-address 192.0.0.0 255.0.0.0 as-set

The last example adds an aggregate route for 192.*.*.* and suppresses advertisements of more specific routes to all neighbors:

XSR(config)#router bgp 23 XSR(config-router)#aggregate-address 192.0.0.0 255.0.0.0 summary-only

Configuring BGP Confederations

The following example configures a confederation comprised of three internal AS’s with AS numbers 1, 2, and 3. To BGP speakers outside the confederation, the confederation appears to be a standard AS with AS number 20 (set with the bgp confederation identifier command).

In a BGP speaker in AS 1, mark the peers from AS’s 2 and 3 as special EBGP peers with the bgp confederation peers command. Peers 192.168.57.5 and 192.168.57.6 then will get the local- preference, next-hop and MED unchanged in updates. The router at 130.32.32.1 is a standard EBGP speaker and the updates it gets from this peer will be similar to a standard EBGP update from a peer in AS 20.

XSR(config)#router bgp 1

XSR(config-router)#bgp confederation identifier 20

XSR(config-router)#bgp confederation peers 2 3

XSR(config-router)#neighbor 192.168.57.5 remote-as 2

XSR(config-router)#neighbor 192.168.57.6 remote-as 3

6-24 Configuring the Border Gateway Protocol