IBGPLearned Route Not Getting Installed in IP Routing Table Cause IBGP Next Hop Not Reachable

The cause of this problem is most common in IBGP-learned routes where BGP next-hop address should have been learned through an Interior Gateway Protocol (IGP). Failure to reach the next hop is an IGP problem, and BGP is merely a victim. With BGP, when IP prefixes are advertised to an IBGP neighbor, the NEXT-HOP attribute of the prefix does not change. The IBGP receiver must have an IP route to reach this next hop.

Figure 15-20 shows the flowchart to follow to resolve this problem.

Figure 15-20. Problem-Resolution Flowchart

Figure 15-20. Problem-Resolution Flowchart

Figure 15-21 shows that NEXT-HOP of BGP routes advertised to IBGP neighbors are not changed and might result in route installation failure.

Figure 15-21. Next hop of BGP Routes Advertised to IBGP Neighbors Is Not Changed and Might Result in Route Installation Failure

Figure 15-21. Next hop of BGP Routes Advertised to IBGP Neighbors Is Not Changed and Might Result in Route Installation Failure

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