Scenario
CoreDNS loop warnings start only after one worker image line moves to a newer Ubuntu release.
A CoreDNS loop appears on one Ubuntu node pool because kubelet still points pods at the generic host stub after resolver changes
Most nodes resolve fine, but one OS image now exposes a different stub resolver path.
What to check first
- Identify the primary failure signal in the One Node Pool Learned a New Stub Address and the Pods Kept Dialing the Old One scenario.
- Separate visible symptoms from the underlying technical dependency.
- Describe the safest recovery path and the follow-up prevention work.
Checking checklist
- Summarize the current impact and the last known change.
- Collect direct evidence from logs, runtime state, and configuration before changing anything.
- Separate immediate recovery from permanent prevention work.
Recovery and prevention
Compare kubelet resolver sources between node pools before restarting CoreDNS.
Questions worth viewing together
No. Keep commands, logs, file names, APIs, and product names unchanged, then explain the reasoning in the selected UI language.
State the root cause, the evidence that supports it, and the safest recovery direction.
The source scenario is treated as an incident artifact. Guidance, checklist, hints, and explanations can be localized around it.
Similar cases seen in the field