Symptoms: BGP Peer Flapping

• The BGP peering session between edge router rtr-edge-01 (AS 65001, 192.168.100.1) and upstream provider rtr-isp-01 (AS 64512, 192.168.100.2) is flapping.
• The session goes down and comes back up every 2-5 minutes.
• When the session drops, all routes learned from the upstream provider are withdrawn, causing a brief outage (~30-60 seconds) for outbound internet traffic until the session re-establishes.
• The BGP event log shows "Hold Timer Expired" as the reason for each session drop.
• The physical link between the two routers is a 1Gbps Ethernet circuit through an ISP-provided media converter.
• Interface error counters on rtr-edge-01 show occasional CRC errors and input errors (~50 per hour).
• The BGP hold timer is set to 15 seconds (keepalive 5 seconds) -- these were set aggressively for "fast failover."
• The problem began after the circuit was migrated to a new media converter last week.