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Network L3 NETWORK-007 · 22 min

A missing ip_forward setting blocks NAT egress after a reboot

Covers a kernel network setting problem that a temporary fix resolves but that breaks again after a reboot.

NetworkFoundation OpsLevel 3Free22 min
Scenario

A scenario that narrows down the root cause, centered on finding where the runtime fix and the persistent setting differ, in the situation of a missing ip_forward setting blocking NAT egress after a reboot.

What to check first
  • Identify the primary failure signal in the Kernel Networking 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
What is the first thing to prove after a reboot NAT incident?

Verify that forwarding state and related persistence settings survived the restart before rewriting firewall rules.