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Scenario #104
Networking
K8s v1.20, GKE

Inconsistent Pod-to-Pod Communication Due to MTU Mismatch

Pod-to-pod communication became inconsistent due to a mismatch in Maximum Transmission Unit (MTU) settings across nodes.

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What Happened

Network packets were being fragmented or dropped due to inconsistent MTU settings between nodes.

Diagnosis Steps
  • 1Verified MTU settings on each node using ifconfig and noticed discrepancies between nodes.
  • 2Used ping with varying packet sizes to identify where fragmentation or packet loss occurred.
Root Cause

MTU mismatch between nodes and network interfaces.

Fix/Workaround
• Aligned MTU settings across all nodes in the cluster.
• Rebooted the nodes to apply the new MTU configuration.
Lessons Learned

Consistent MTU settings are crucial for reliable network communication.

How to Avoid
  • 1Ensure that MTU settings are consistent across all network interfaces in the cluster.
  • 2Test network connectivity regularly to ensure that no fragmentation occurs.
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