Discussion

Here’s the complete IBGP group configuration on RouterG:
[edit protocols bgp]
aviva@RouterG# show
group internal-within-AS65500 {
type internal;
local-address 192.168.19.1;
cluster 192.168.19.1;
neighbor 192.168.13.1;
neighbor 192.168.12.1;
neighbor 192.168.17.1;
neighbor 192.168.15.1;
neighbor 192.168.16.1;
}
You still need to configure all the IBGP neighbors, both those within the cluster
(192.168.13.1 and 192.168.12.1) and the three IBGP peers outside the cluster. For
the nonclient routers, those outside the cluster, you include the route reflector in the
IBGP group but don’t need to have neighbor statements for the routers within the
cluster. On the client routers, you need to configure only one IBGP peer, the route
reflector 192.168.19.1:
[edit protocols bgp]
aviva@RouterA# show
group cluster-within-AS65500 {
type internal;
local-address 192.168.13.1;
neighbor 192.168.19.1;
}
This configuration is a lot simpler than having to specify all the IBGP neighbors.
Another advantage from the point of view of the routers’ configurations is if you later
add routers to the cluster, you do not need to change the configuration on the existing
client routers in the cluster.
The nonclient routers in the AS, RouterE and RouterF, need to establish an IBGP
session with RouterG but they don’t need sessions with RouterA or RouterB. In this
small network, this is a savings of four TCP sessions and four IBGP peerings. Again,
if you add routers to the cluster, the IBGP group configuration on the nonclient routers
doesn’t need to change.
All the client routers in the cluster and all the nonclient routers are in the same AS,
so make sure that you configure them all with the same AS number:
[edit routing-options]
aviva@RouterB# show
autonomous-system 65500;
Looking at the routes that RouterBhas learned, you see that it still knows how to
reach routes in AS 65505:
aviva@RouterB> show route protocol bgp
inet.0: 21 destinations, 22 routes (21 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
454 | Chapter 13: BGP
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