Kubernetes Online Training - Docker Online Training
                     Troubleshooting 
Kubernetes 
Network Issues
A Comprehensive Guide
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Understanding Kubernetes Networking
 Kubernetes relies on networking for pod-to-pod 
communication, services, and external traffic.
Key Components:
o Pod Networking (Unique IP per pod)
o Service Networking (Abstracts pod communication)
o Ingress & Egress (Traffic entering or leaving the cluster)
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Diagnosing Pod-to-Pod Communication
 Verify Pod IPs: Use kubectl get pods -o 
wide to check pod IPs.
 Connectivity Tests: Use ping or curl within 
pods to check if they can reach other pods.
• Network Policies: Ensure that network 
policies aren't blocking communication.
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Examining Services and Endpoints
 Service Configuration: Use kubectl describe svc 
 to verify service details.
 Endpoints: Ensure services are correctly linked to pods 
via kubectl get endpoints .
• DNS Issues: Verify CoreDNS logs to ensure DNS 
resolution is working.
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Troubleshooting Ingress & Egress Traffic
 Ingress Configuration: Ensure ingress 
controllers are properly set up.
 Egress Traffic: Review network policies 
related to traffic leaving the cluster.
• Check Logs: Review logs of ingress 
controllers and egress configurations.
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Inspecting the CNI (Container Network Interface)
 CNI Plugins: Ensure the CNI plugin (e.g., Calico, 
Flannel) is running properly.
 Configuration Files: Verify CNI configuration in 
/etc/cni/net.d/.
• Logs: Check CNI-related logs for errors or network 
issues.
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Resource Constraints & Node Pressure
 Monitor Resource Usage: Use kubectl top pods 
or kubectl top nodes to track CPU and memory.
 Node Resources: Ensure nodes have enough 
available resources to run networking 
components smoothly.
• Throttling: Check for throttling or over-
commitment on nodes.
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Reviewing Cluster Logs
 Kubelet Logs: Check journalctl -u kubelet for pod 
lifecycle issues.
 API Server Logs: Review control plane logs for issues in 
service or pod communication.
• CoreDNS Logs: Check logs for DNS resolution 
problems.
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Network Performance & Latency
 Monitoring Tools: Use tools like Weave Scope, 
Prometheus, and Grafana to monitor network 
performance.
 Latency & Packet Loss: Investigate any issues 
related to high latency, packet loss, or bandwidth 
throttling.
• Troubleshoot Performance: Visualize traffic 
and pinpoint performance bottlenecks.
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