Illustrative operator finding
Likely lead to testA physical link or port problem on SW2 Gi0/1.
- Why this lead?
- The error counters change before anything else, on the same port that then flaps. The routing symptoms on R2 follow, which fits reconvergence after a link loss rather than a routing fault.
- Suggested checks
- Inspect the transceiver, cabling and error counters on SW2 Gi0/1.
- Confirm the state of the connected upstream device.
- Watch the BGP session on R2 once the link is stable.
- Alternative to check
- A planned change on SW2 or R2 could produce the same pattern. Check change records for the window before replacing hardware.