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Scenario #178
Networking
K8s v1.21, AWS EKS
Pod Network Degradation Due to Overlapping CIDR Blocks
Network degradation occurred due to overlapping CIDR blocks between VPCs in a hybrid cloud setup, causing routing issues.
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What Happened
In a hybrid cloud setup, the CIDR blocks of the Kubernetes cluster VPC and the on-premise VPC overlapped, causing routing issues that led to network degradation and service disruptions.
Diagnosis Steps
- 1Investigated network routes using kubectl describe node and confirmed overlapping CIDR blocks.
- 2Verified routing tables and identified conflicts causing packets to be misrouted.
Root Cause
Overlapping CIDR blocks between the cluster VPC and the on-premise VPC caused routing conflicts.
Fix/Workaround
• Reconfigured the CIDR blocks of one VPC to avoid overlap.
• Adjusted the network routing tables to ensure traffic was correctly routed.Lessons Learned
Ensure that CIDR blocks are carefully planned to avoid conflicts in hybrid cloud environments.
How to Avoid
- 1Plan CIDR blocks in advance to ensure they do not overlap.
- 2Review and validate network configurations during the planning phase of hybrid cloud setups.