%BGP-5-ADJCHANGE: neighbor 203.0.113.1 Down BGP Notification sent
In plain English: A BGP session — the connection that exchanges routes with a neighboring network — dropped.
Platform: Cisco IOS / IOS XE routers (BGP state machine per RFC 4271).
What it means
A BGP session — the connection that exchanges routes with a neighboring network — dropped. The words after 'Down' name the reason BGP itself recorded: 'User reset' means someone cleared it, 'Hold Timer Expired' means the other side went silent, 'Peer closed the session' means the far end ended it. When it says 'Up' a few minutes later, the session recovered — but routes flapped, and traffic may have moved.
Likely causes, in order
The other router rebooted, lost power, or its link failed.
Someone changed BGP configuration on either side ('User reset' in the message is the fingerprint).
The path between the two routers broke — BGP rides on a normal TCP connection, and anything that kills the path kills the session.
The link got so congested that BGP's keepalive messages could not get through before the hold timer ran out.
Check, in order
show ip bgp summaryThe neighbor's current state: Established is healthy. Active or Idle means the session is still broken right now.
show ip bgp neighbors 203.0.113.1Look for 'Last reset' and the reason recorded there — it repeats what the log said, with counters.
show logging | include BGPLine up every Down/Up pair. A session that drops every few minutes is a different problem from one drop during a maintenance window.
The fix
If the state is Established and prefixes are flowing, the incident is over — find the reason in the logs and the other side's change calendar before closing it.
If it is stuck in Active, work the connection problem, not BGP itself — see the full case linked below.
If 'Hold Timer Expired' repeats on a busy link, protect BGP traffic with QoS or fix the congestion; do not just raise the timers to hide it.
Did this fix it for you? One tap — anonymous, nothing to type, and nothing you send is ever published.
Thanks — your tap helps the next engineer. A run of "still broken" reports sends this page back to the top of our re-check list.
Full case: this error is one stop in a bigger fault. Work the complete playbook: BGP Neighbor Stuck in Active — checks, ranked causes, the fix, and verification.