HSRP split behavior appears after trunk allowed list drops the failover VLAN

Gateway redundancy works on most VLANs, but one subnet loses predictable failover because the standby control traffic no longer crosses the trunk everywhere it should.

이 문제의 전체 시나리오와 점검 체크리스트, 복구 순서, 모범 풀이는 Pro 구독에서 열립니다.

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• Identify the primary failure signal in the Gateway Redundancy scenario.
• Separate visible symptoms from the underlying technical dependency.
• Describe the safest recovery path and the follow-up prevention work.

1. Summarize the current impact and the last known change.
2. Collect direct evidence from logs, runtime state, and configuration before changing anything.
3. Separate immediate recovery from permanent prevention work.

Choose the smallest safe recovery action first, then record the prevention work that reduces repeat incidents.