BGP session flap with Cogent in Amsterdam (AMS1)

Affected:

Network · AMS1

Duration

38 min

Reference

inc-20250629-1

Timeline

1. Resolved29 Jun 2025, 21:23 UTC

   Resolved. Total impact: intermittent reroutes for about 38 minutes; no session was lost on customer servers.

2. Monitoring29 Jun 2025, 21:11 UTC

   The session has been stable for 20 minutes after the carrier corrected the interface configuration.

3. Identified29 Jun 2025, 20:58 UTC

   The flap is caused by an MTU mismatch introduced during a carrier-side change. The session is administratively shut while it is corrected.

4. Investigating29 Jun 2025, 20:45 UTC

   One of our BGP sessions with Cogent in Amsterdam (AMS1) is flapping. Some destinations may see brief reroutes and increased latency.

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