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Scenario #111
Networking
K8s v1.21, GKE

DNS Resolution Failure Due to Incorrect Pod IP Allocation

DNS resolution failed due to incorrect IP allocation in the cluster’s CNI plugin.

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What Happened

Pods were allocated IPs outside the expected range, causing DNS queries to fail since the DNS service was not able to route correctly.

Diagnosis Steps
  • 1Reviewed the IP range configuration for the CNI plugin and verified that IPs allocated to pods were outside the defined CIDR block.
  • 2Observed that pods with incorrect IP addresses couldn’t register with CoreDNS.
Root Cause

Misconfiguration of the CNI plugin’s IP allocation settings.

Fix/Workaround
• Reconfigured the CNI plugin to correctly allocate IPs within the defined range.
• Re-deployed affected pods with new IPs that were correctly assigned.
Lessons Learned

Always verify IP range configuration when setting up or scaling CNI plugins.

How to Avoid
  • 1Check IP allocation settings regularly and use monitoring tools to track IP usage.
  • 2Ensure CNI plugin configurations align with network architecture requirements.
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