Ubuntu 18.04 LTS Kubernetes Node NotReady Due to CNI Issues

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Node enters NotReady state and workloads cannot schedule or communicate reliably.

Environment & Reproduction

Ubuntu 18.04 kubelet nodes after CNI plugin update mismatch or network policy changes.

Root Cause Analysis

CNI binaries, config files, or kernel networking prerequisites are missing or inconsistent.

Quick Triage

Inspect kubelet logs and CNI pod status to confirm plugin initialization failures.

Step-by-Step Diagnosis

Check /etc/cni configs, plugin binary versions, iptables mode, and container runtime networking integration.

Solution – Primary Fix

Align CNI plugin and config versions, reload kubelet/runtime, and revalidate cluster network policy behavior.

Solution – Alternative Approaches

Cordoning and replacing node can be faster when local networking state is badly corrupted.

Verification & Acceptance Criteria

Node returns Ready and pod network tests succeed across namespaces.

Rollback Plan

Revert to previous CNI manifest and plugin build if new deployment fails.

Prevention & Hardening

Version-lock CNI components and test cluster networking changes in canary nodes first.

Related Errors & Cross-Refs

Related issues include kube-proxy iptables conflicts and MTU mismatch packet drops.

Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.

View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Review Kubernetes CNI plugin docs and Ubuntu container networking references.