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Kubernetes imposes the following fundamental requirements on any networking implementation

  • all containers can communicate with all other containers without NAT
  • all nodes can communicate with all containers (and vice-versa) without NAT
  • the IP that a container sees itself as is the same IP that others see it as

Important CIDR Ranges

  • Cluster CIDR: IP Range used to assign IPs to pods in the cluster
  • Service Cluster IP Range: IP Range for services in the cluster This should not overlap with the cluster CIDR range
  • Pod CIDR: IP range for pods on a specific worker node. This range should fall within the cluster CIDR but not overlap with the pod CIDR of any other worker node. Normally, the networking plugin will automatically handle the IP aloocation