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Network L4 NETWORK-065 · 19 min

Root guard errdisables the uplink after temporary loop prevention during maintenance

The spanning-tree design is mostly correct, but a maintenance path unexpectedly presents a superior BPDU and the protected uplink shuts itself down.

NetworkFoundation OpsLevel 4Free19 min
Scenario

The spanning-tree design is mostly correct, but a maintenance path unexpectedly presents a superior BPDU and the protected uplink shuts itself down.

What to check first
  • Identify the primary failure signal in the Layer 2 Guard Trigger 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.