Routing - BGP Route Filter with Debug - Reject Routes

 

This Blog is related with how BGP will rejecting Route using Route Filter 

Created Route-Map 

R6#sh route-map Block-in

route-map Block-in, permit, sequence 10

  Match clauses:

    ip address prefix-lists: Block

  Set clauses:

  Policy routing matches: 0 packets, 0 bytes

Created Prefix List to Block Some Routes 

R6#sh ip prefix-list Block

ip prefix-list Block: 2 entries

   seq 5 deny 1.1.1.0/24

   seq 10 permit 0.0.0.0/0 ge 1

Validate 

R6#sh ip pro

Routing Protocol is "bgp 200"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  IGP synchronization is disabled

  Automatic route summarization is disabled

  Redistributing: connected

  Neighbor(s):

    Address          FiltIn FiltOut DistIn DistOut Weight RouteMap

    10.10.10.10

    192.168.46.4                                          Block-in

  Maximum path: 1

  Routing Information Sources:

    Gateway         Distance      Last Update

    192.168.46.4          20      00:14:11

  Distance: external 20 internal 200 local 200

DEBUG LOGS SAYS HOW IT WORKS

*Mar  1 00:37:28.183: BGP(0): start inbound soft reconfiguration for 192.168.46.4

*Mar  1 00:37:28.183: BGP(0): process 1.1.1.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.183: BGP(0): Prefix 1.1.1.0/24 rejected by inbound route-map.

*Mar  1 00:37:28.187: BGP(0): update denied

*Mar  1 00:37:28.187: BGP(0): process 2.2.2.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.187: BGP(0): process 3.3.3.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.191: BGP(0): process 4.4.4.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.191: BGP(0): process 172.16.1.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.195: BGP(0): process 192.168.12.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.195: BGP(0): process 192.168.13.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.199: BGP(0): process 192.168.24.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.199: BGP(0): process 192.168.34.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.199: BGP(0): process 192.168.45.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.199: BGP(0): process 192.168.46.0/24, next hop 192.168.46.4, metric 0 from 192.168.46.4

*Mar  1 00:37:28.199: BGP(0): complete inbound soft reconfiguration, ran for 16ms

*Mar  1 00:37:28.643: BGP: 10.10.10.10 active open failed - no route to peer, open active delayed 29134ms (35000ms max, 28% jitter)

R6#