In this post, we’ll explore the Weaveworks Weave CNI plugin and its role in Kubernetes networking. Previously, we replaced a custom CNI script with the Weave plugin. Now, let’s understand how it works and why it’s effective for larger environments.

Manual Networking Recap

In smaller setups, we manually configured routing tables to map networks to specific nodes. While this approach works for simple networks, it doesn’t scale well as clusters grow. Managing hundreds of nodes and thousands of pods requires a more sophisticated solution, like Weave.

How the Weave CNI Plugin Works

The Weave CNI plugin simplifies Kubernetes networking by creating a decentralized system where nodes automatically share networking information.

CNI Weave

  1. Weave Agents:

    • Weave installs an agent on each node in the cluster.
    • These agents communicate with each other, maintaining a topology of all nodes, pods, and their IPs.

  2. Bridge Networks:

    • Weave creates a weave bridge on each node to manage pod networking.
    • Pods are configured with routes to the Weave agent, ensuring seamless communication between nodes.

  3. Packet Encapsulation:

    • When a pod communicates with another pod on a different node, Weave encapsulates the packet for transport across the network.
    • The destination node decapsulates the packet and routes it to the target pod.

Deploying Weave in Kubernetes

Deployment Options

  • Manual Deployment: Deploy Weave agents as daemons on each node.
  • Pod Deployment: Deploy Weave as pods using Kubernetes.

DaemonSet Deployment

  • The recommended method is to deploy Weave as a DaemonSet.
  • A DaemonSet ensures that a Weave pod runs on every node in the cluster.

Single Command Deployment

Once the Kubernetes cluster is operational:

kubectl apply -f https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')

This deploys all necessary components, including the Weave DaemonSet.

Troubleshooting Weave

To debug issues with Weave, use the following commands:

Check Weave Pods:

kubectl get pods -n kube-system

View Logs:

kubectl logs <pod-name> weave -n kube-system