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BGP stuck in Active

A neighbor stuck in Active means your router keeps trying to open the BGP session and the peer never answers in a way that completes it. BGP runs over TCP 179, so 'Active' almost always points at a layer-3/4 problem or a parameter mismatch, not BGP policy.

What it means

BGP cycles Idle → Connect → Active as it tries to establish. Sitting in Active means the outbound TCP connection isn't completing. You want to reach Established; anything else means no routes are exchanged.

Most common causes

  • Wrong remote-AS. Your `neighbor x.x.x.x remote-as N` doesn't match the AS the peer is actually in. The session never forms.
  • No IP reachability to the peer. If you can't ping the neighbor's BGP source address, TCP 179 can't connect either. Check the link and any /30 addressing.
  • TCP 179 blocked. An ACL or firewall dropping TCP 179 in either direction will hold the session in Active.
  • Wrong update-source or peer not configured. If one side sources from a loopback the other doesn't expect, or the peer has no matching neighbor statement, it never establishes.

How to fix it

  1. Ping the neighbor's BGP address. No reply means fix reachability first.
  2. Compare `remote-as` on both routers against each side's actual local AS.
  3. Run `show ip bgp summary` and watch the state, and confirm the neighbor IP is exactly right.
  4. Confirm both routers have a neighbor statement pointing at each other.
  5. Check for ACLs touching TCP 179 on the path.