BGP identifier wrong 4 bytes error on Cisco router

While studying on the topic of BGP, border gateway protocol. I tested out the lab scenario from the Cisco.com site about BGP with Two Different Service Providers (Multihoming). After peering the 2nd ISP, I notice errors popping up. Upon checking I notice the “BGP router identifier” for the R2 and R4 were identical. I went into the R4 and issue the command “bgp router-id x.x.x.x” and the adjacency formed :)

This happened because on both router I had similar loopback interface which have same ip address assigned :)

Find out how does the BGP select the router ID [LINK]

R2 error message
R2#*Mar  1 04:10:38.698: %BGP-3-NOTIFICATION: sent to neighbor 10.0.20.2 2/3 (BGP identifier wrong) 4 bytes C0A8C801
R2#FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 002D 0104 00C8 00B4 C0A8 C801 1002 0601 0400 0100 0102 0280 0002 0202 00

R4 error message
R2#*Mar  1 00:51:04.823: %BGP-3-NOTIFICATION: sent to neighbor 10.0.20.1 2/3 (BGP identifier wrong) 4 bytes C0A8C801
R4#FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 002D 0104 012C 00B4 C0A8 C801 1002 0601 0400 0100 0102 0280 0002 0202 00

R2#sh ip bgp summary
BGP router identifier 192.168.200.1, local AS number 300

R4#sh ip bgp summary
BGP router identifier 192.168.200.1, local AS number 200

June 3, 2011 | Filed Under Network | Leave a Comment 
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