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Scenario #181
Networking
K8s v1.22, AWS EKS

Pod-to-Pod Communication Failure Due to CNI Plugin Configuration Issue

Pods were unable to communicate with each other due to a misconfiguration in the CNI plugin.

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What Happened

The Calico CNI plugin configuration was missing the necessary IP pool definitions, which caused pods to fail to obtain IPs from the defined pool, resulting in communication failure between pods.

Diagnosis Steps
  • 1Ran kubectl describe pod to identify that the pods had no assigned IP addresses.
  • 2Inspected the CNI plugin logs and identified missing IP pool configurations.
Root Cause

The IP pool was not defined in the Calico CNI plugin configuration, causing pods to be unable to get network addresses.

Fix/Workaround
• Updated the Calico configuration to include the correct IP pool definitions.
• Restarted the affected pods to obtain new IPs.
Lessons Learned

Always verify CNI plugin configuration, especially IP pool settings, before deploying a cluster.

How to Avoid
  • 1Automate the verification of CNI configurations during cluster setup.
  • 2Test network functionality before scaling applications.
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