BGP: Rejected Incoming Prefix
3142
Created On 05/10/22 04:07 AM - Last Modified 06/06/24 04:39 AM
Question
What is BGP's rejected incoming prefix
Environment
- PAN-OS
- BGP
Answer
TOPOLOGY:
Take note that there are two prefixes announced to FW_2:
- 10.10.10.0/24 has a BGP next-hop attribute of 192.168.1.1, which is a host directly connected to one of FW_2's interface
- 10.10.20.0/24 has a BGP next-hop attribute of 172.16.1.1, a host route that FW_2 is unaware of.
FW_2's TABLE RESULT:
The above shows FW_2's BGP table. Comparing the two routes received and installed in the BGP table:
- Prefix 10.10.10.0/24 has an asterisk next to it, and it would mean that the prefix has been verified to pass the route verification process, which is to do a route recursion of the next-hop attribute.
- Prefix 10.10.20.0/24 has failed the route recursion lookup of its next-hop attribute since FW_2 has no route leading to 172.16.1.1
The above shows FW_2's BGP summary table. Highlighted in Incoming Prefix is the Rejected count number.
Due to the route recursion lookup failure for prefix 10.10.20.0/24, which leads to the BGP table rejecting it, the routing table won't be able to learn and install the said prefix.