Check the BGP configuration on the remote devices to ensure that the neighbor IP
addresses, AS numbers, and other configuration parameters match.
Ensure that the VPN tunnel is up and that the internet connectivity of both
sites is stable. If the VPN tunnel isn't stable or the Internet connection is
unreliable, contact your ISP to troubleshoot the connection issues.
Verify the status of BGP peering, and verify that the neighbor is in the ethe
established state. If not, note the status and error message (if any).
Ensure that the two BGP peers can reach each other over the VPN tunnel. You can
use
ping
or
traceroute
for this step. If
the tunnel is up but you can't ping the peer, confirm that routing is in place
for the peering to establish as expected.
Take a packet capture. This could be helpful to identify any issues with the BGP
messages exchanged or to verify whether BGP messages are traversing the VPN
tunnel as expected. Capture traffic on the appropriate interface and filter for
BGP traffic (TCP port 179).
Check the remote device logs for any BGP-related messages. Look for any errors
or subcodes that might provide a reason for the down event.
