Information Technology Reference
In-Depth Information
Example 8-33
BGP RIB on R4 (Continued)
*> 192.168.14.1 0 100 0 (100) i
*>i192.168.201.0 192.168.100.6 0 100 0 i
* 192.168.202.0 192.168.100.7 0 100 0 (100) i
*> 192.168.14.1 0 100 0 (100) i
This temporary forwarding loop is formed only if the next hop is reset on R1 for all the pre-
fixes, as indicated previously in Step 4. So the solution is to not reset next hops for sessions
between member autonomous systems. You can do this by putting the link between R1 and
R8 into IS-IS when the same IGP is used for the entire confederation, or by resetting the
next hops only for eBGP learned routes on R1.
Step 6: Move R7 from Member AS 100 to Member AS 65001 and Move R5 out of the
Forwarding Paths
Move R7 from member AS 100 to member AS 65001, which is service-affecting for the
prefix originated locally on the router. Example 8-34 shows the new BGP configurations
on R7.
Example 8-34
BGP Configurations on R7
router bgp 65001
no synchronization
bgp router-id 192.168.100.7
bgp log-neighbor-changes
bgp confederation identifier 100
bgp confederation peers 100 65000
network 192.168.202.0
neighbor Internal peer-group
neighbor Internal remote-as 65001
neighbor Internal update-source Loopback0
neighbor 192.168.100.4 peer-group Internal
neighbor 192.168.100.5 peer-group Internal
neighbor 192.168.100.6 peer-group Internal
no auto-summary
To prepare the migration of R5 (in the next step) and to avoid traffic loss, you should move
R5 out of the forwarding paths by increasing IGP metrics to R5. Because R4 has reachabil-
ity to all prefixes, traffic forwarding is unaffected. The current network topology is shown
in Figure 8-6.
