Ever since a recent firewall change at your WAN/lnternet edge, the 8GP state in your...

The BGP state on a VSX pair is stuck (not 'Established') after a recent firewall change at the WAN/Internet edge, where the BGP peering likely occurs.

BGP and Firewalls:BGP establishes sessions usingTCP port 179. Firewalls located between BGP peers must explicitly permit TCP port 179 traffic bidirectionally for the peering to establish and maintain. Firewall changes are a frequent cause of broken BGP sessions.

Troubleshooting Steps After Firewall Change:The most logical first step is to verify that the firewall change did not inadvertently block TCP port 179 between the configured BGP neighbor IP addresses.

Analysis of Options:

A: Restarting routing service is disruptive and not the first step.

B: Confirming that appropriate TCP ports (specifically 179) are still allowed through the firewall directly addresses the most probable cause related to the firewall change event.

C: Restarting NAT service is likely irrelevant unless NAT is incorrectly configured for BGP peers.

D: Confirming the peer AS is a basic configuration check but less likely related to thefirewall changeevent than port blocking.

Conclusion:Given the problem occurred immediately following a firewall change, verifying that the firewall still permits TCP port 179 between the BGP peers is the most direct and likely troubleshooting step.