• k8s
• StudyNotes
• k8sNetworking

k8s/StudyNotes/k8sNetworking

• CNI - specifies that kubelet should call CNI plugin on container create(ADD) and destroy(DEL)

  • Config

     /usr/bin/kubelet --cni-bin-dir=/opt/cni/bin --cni-conf-dir=/etc/cni/net.d/ --network-plugin=cni 

• Docker uses default bridge docker0
  • Docker creates network namespace (ip netns ) for each container. $ docker inspect abcd

• CNI - plugins e.g. bridge

  bridge add <containerid> /var/run/netns/2e34dc

  • JSON Network config, ADD and DEL between runtime and plugin.
• k8s ports in documentation
• Services - across cluster pod access
  • Virtual object created by kube-proxy, IP from pre-assigned range, iptables fwd to pod ip.

    • Service ip range kube-api-server --service-cluster-ip-range= ipNet )Default:10.0.0.0/24)

      • service ip range can't overlap with pod ip range

    • View  iptables -L -t nat | grep <service> 

    • kube-proxy --proxy-mode ["userspace", "iptables", "ipvs"]

      • view  cat /var/log/kube-proxy.log 

  • Types
    1. ClusterIP - only available in cluster

    2. NodePort - Just like ClusterIP, but also exposes to fixed external port on all nodes
  • How
    • kube-proxy watches kube-apiserver,