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Network L2 NETWORK-014 · 18 min

The port is open but a reverse path filter keeps the response from returning

A situation where incoming connections are visible but response packets are blocked by kernel policy, so the session never establishes.

NetworkFoundation OpsLevel 2Free18 min
Scenario

A scenario that narrows down the root cause, centered on understanding an asymmetric network where the incoming path and outgoing path differ, in the situation of the port being open but a reverse path filter keeping the response from returning.

What to check first
  • Identify the primary failure signal in the Kernel Route Filter 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

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

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.