KubeFM

Learned it the hard way: don't use Cilium's default Pod CIDR, with Isala Piyarisi

Feb 25, 2025

32:30

This episode examines how a default configuration in Cilium CNI led to silent packet drops in production after 8 months of stable operations.

Isala Piyarisi, Senior Software Engineer at WSO2, shares how his team discovered that Cilium's default Pod CIDR (10.0.0.0/8) was conflicting with their Azure Firewall subnet assignments, causing traffic disruptions in their staging environment.

You will learn:

How Cilium's default CIDR allocation can create routing conflicts with existing infrastructure
A methodical process for debugging network issues using packet tracing, routing table analysis, and firewall logs
The procedure for safely changing Pod CIDR ranges in production clusters

Sponsor

This episode is sponsored by Learnk8s — get started on your Kubernetes journey through comprehensive online, in-person or remote training.

More info