When R2 is configured with wrong AS Number, lets se the error message sent by R1 and received by R2 –
*Mar 1 00:27:09.287: %BGP-3-NOTIFICATION: sent to neighbor 192.168.12.2 2/2 (peer in wrong AS) 2 bytes 0014
*Mar 1 00:28:37.991: %BGP-3-NOTIFICATION: received from neighbor 192.168.12.1 2/2 (peer in wrong AS) 2 bytes 0014
As seen from the output logs on R1 and R2, where R1 sends the notification and R2 receives the notification on incorrect AS number (shown in HEX as “0014”) which comes out to be BGP ASN “20” in decimal.
Now that we know R2 has been wrongly configured as BGP AS 20 instead of 2 , the administrator can perform any of below options to address the problem scenario –
Option 1 –
Change the BGP configuration on R2 ie remove “Router BGP 20” and replace whole configuration on “Router BGP 2”
No router bgp 20
router bgp 2
net 18.104.22.168 m 255.255.255.0
neighb 192.168.12.1 remote-as 1
Option 2 –
On R1 , configure neighbor command with “Remote-as” of R2 being 20 instead of 2-
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