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Scenario #173
Networking
K8s v1.21, GKE
Dropped Network Packets Due to MTU Mismatch
Network packets were dropped due to a mismatch in Maximum Transmission Unit (MTU) settings across different network components.
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What Happened
Pods experienced connectivity issues and packet loss because the MTU settings on the nodes and CNI plugin were inconsistent, causing packets to be fragmented and dropped.
Diagnosis Steps
- 1Used ping and tracepath tools to identify dropped packets and packet fragmentation.
- 2Inspected the CNI plugin and node MTU configurations and found a mismatch.
Root Cause
Inconsistent MTU settings between the CNI plugin and the Kubernetes nodes caused packet fragmentation and loss.
Fix/Workaround
• Unified MTU settings across all nodes and the CNI plugin configuration.
• Restarted the network components to apply the changes.Lessons Learned
Ensure consistent MTU settings across the entire networking stack in Kubernetes clusters.
How to Avoid
- 1Automate MTU validation checks during cluster setup and upgrades.
- 2Monitor network packet loss and fragmentation regularly.