BGP Route Not Getting Originated Cause BGP Is Autosummarizing to Classful Network Boundary

Sometimes, classful networks are advertised in BGP when other routing protocols are redistributed in BGP. For example, BGP might be trying to redistribute 100.100.100.0/24, but only 100.0.0.0/8 gets advertised. Another example could be that 131.108.0.0/16 is advertised where 131.108.5.0/24 was redistributed.

BGP autosummarizes subnetted routes to their network boundaries when redistributed into BGP from any other routing protocol. For example, subnetted Class A routes automatically are summarized to the Class A mask /8 when redistributed in BGP from any other protocol.

Figure 15-11 shows the flowchart to follow to fix this problem.

Figure 15-11. Problem-Resolution Flowchart

Figure 15-11. Problem-Resolution Flowchart

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