System information

Configuring BGP
12-27
In the network shown in Figure 12-10, Router San Francisco advertises network
172.56.0.0 to Router Miami with a next hop attribute of 172.56.20.1. Router Miami
advertises network 120.80.0.0 to Router San Francisco with a next hop attribute of
172.56.20.2.
In BGP, the next hop of EBGP-learned routes is carried without modification in IBGP.
Because of this BGP rule, Router Miami advertises 172.56.0.0 to its IBGP peer
(Router New York) with a next hop attribute of 172.56.20.1. As a result, according to
Router New York, the next hop to reach 172.56.0.0 is 172.56.20.1 instead of
130.60.20.1 via an IGP. Router New York drops packets destined for 171.56.0.0, if
this next hop 172.56.20.1 is not reachable via IGP.
Figure 12-10 Configuring Next Hop Processing
The following commands configure Router Miami:
MOT(config)#router bgp 100
MOT(config-bgp)#neighbor 172.56.20.1 remote-as 300
MOT(config-bgp)#neighbor 120.80.30.2 remote-as 100
MOT(config-bgp)#network 130.60.0.0
AS 100
AS 300
172.56.20.1
SF
Washington
NY
EBGP
IBGP
Miami
172.56.20.1
172.56.20.2
120.80.30.2
130.60.20.1