Discussion

AS 65500
RouterF
192.168.16.1
RouterD
192.168.14.1
AS 65505
RouterE
192.168.15.1
RouterJ
192.168.17.1
RouterH
192.168.18.1
RouterJ
192.168.11.1
Figure 13-2. IBGP network
directly connected to and the ones that it is not directly connected to. These neighbor
statements effectively create the full-mesh peering among all the IBGP routers. For
IBGP peers, when you specify the addresses, you don’t use the physical interface but
rather the loopback address of the router. You can do this because even if a link to
the router is down, it might still be reachable through the IGP. Finally, the localaddress
statement sets the loopback address as the source address of all IP packets
sent by BGP to all destination routers.
The configuration for all the IBGP routers is basically the same, with each router
using the appropriate local address and listing all the other IBGP routers in the AS as
neighbors.
Define the AS number and router ID on each IBGP router just as you did on the border
router:
[edit routing-options]
aviva@RouterE# set autonomous-system 65500
aviva@RouterE# set router-id 192.168.15.1
Be sure to configure the same AS number on all the IBGP routers.
Finally, an IGP must run among all the IBGP routers. For the examples in this chapter,
we use a simple OSPF configuration. Here is the configuration on RouterF, the
border router:
[edit protocols]
aviva@RouterF# show ospf
area 0.0.0.0 {
interface lo0.0 {
passive;
}
interface t1-0/0/2.0;
interface fe-0/0/1.0;
}
When all routers are configured for the IBGP mesh, use the show bgp summary command
to check that all the sessions are up and running. Here’s what you see on one
of the internal routers:
432 | Chapter 13: BGP
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