Information Technology Reference
In-Depth Information
At this stage, there is no BGP redundancy in part of the network. This is because the ses-
sions between R4 and R7, between R5 and R6, and between R4 and R5 are still down. The
current topology is shown in Figure 8-5.
Figure 8-5
Current Network Topology
AS 200
R8
172.16.0.0/16
AS 65001
AS 100
R1
R4
192.168.201.0/24
192.168.200.0/24
R6
R3
R2
R7
R5
192.168.202.0/24
Confederation 100
If
next-hop-self
is used for the session between R1 and R4 (the third option in Step 4), there
is a potential forwarding loop between R1 and R4. Example 8-33 shows the BGP RIB on
R4. Besides the route from R6, all other prefixes are learned via the member AS 100. Note
that the BGP next hop for 192.168.202.0 is R1 for the path learned from R1 (the best path).
A forwarding loop is formed between R1 and R4 for the prefix, because R4 is also one of
the two IGP next hops from R1 to reach R7.
Example 8-33
BGP RIB on R4
R4#show ip bgp
BGP table version is 8, local router ID is 192.168.100.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 172.16.0.0 192.168.100.1 0 100 0 (100) 200 i
*> 192.168.14.1 0 100 0 (100) 200 i
* 192.168.200.0 192.168.100.3 0 100 0 (100) i
continues
