Information Technology Reference
In-Depth Information
Example 4-49
BGP RIB on R7 (Continued)
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 172.15.0.0 192.168.57.5 0 300 100 2 i
*> 192.168.47.4 0 200 100 100 i
*> 172.16.0.0 0.0.0.0 0 32768 i
The resulting topology is shown in Figure 4-12.
Figure 4-12
Topology After R2 Is Migrated to AS 2
AS 400
R7
172.16.0.0/16
172.16.0.0/16
AS 300
AS 200
R4
R5
R6
Local-as 100
no-prepend
172.15.0.0/16
AS 2
172.15.0.0/16
172.15.0.0/16
R1
R2
R3
AS 100
The next step is to migrate R1 to the new AS. Local AS is configured on R1 on the session
with R4. AS_PATH prepending is now removed on R1. The LOCAL_PREF is modified to
prefer the path via R4. The reason that LOCAL_PREF is used instead of WEIGHT is that
R2 would also prefer the path via R1 for 172.16.0.0/16 if the link between R2 and R5 failed.
The new BGP configurations on R1 and R2 are shown in Examples 4-50 and 4-51,
respectively.
Example 4-50
BGP Configuration on R1
router bgp 2
network 172.15.0.0
neighbor 192.168.12.2 remote-as 2
neighbor 192.168.14.4 remote-as 200
neighbor 192.168.14.4 local-as 100
continues
