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Network L5 NETWORK-1486 · 11 min

A Palo Alto HA failover succeeds and inbound traffic still dies because the ARP suppression cache on the adjacent switch outlives the gratuitous update burst

The firewall pair is healthy, but the neighboring switch ignores the failover advertisement long enough to blackhole new flows.

NetworkFoundation OpsLevel 5Free11 min
Scenario

Inbound traffic drops briefly after firewall failover even though the HA pair reports a clean transition.

What to check first
  • Identify the primary failure signal in the The Active Node Changed and the Neighbor Kept Trusting the Last Owner of the Address scenario.
  • Separate visible symptoms from the underlying technical dependency.
  • Describe the safest recovery path and the follow-up prevention work.
Checking checklist
  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.
Recovery and prevention

Inspect neighbor ARP behavior before tuning HA timers.

Questions worth viewing together
Should I translate commands, logs, or product names?

No. Keep commands, logs, file names, APIs, and product names unchanged, then explain the reasoning in the selected UI language.

What should the answer focus on?

State the root cause, the evidence that supports it, and the safest recovery direction.

Why can the scenario remain in the original language?

The source scenario is treated as an incident artifact. Guidance, checklist, hints, and explanations can be localized around it.