Internal

Overview

UDP 4789, node to node, node to master and master to node: must be accessible for any host in the cluster, it is required for SDN communication between pods on separated hosts.
TCP 53 or 8053, node to master, master to master: used by internal DNS traffic.
TCP 8443 node to master: access to API.
TCP 10250 master to node: a node endpoint to be used by the master for communication.
TCP 2379, 2380, 4001 master to master: used by clustered etcd. 2379 is used for state change traffic, 2380 is used for leader election and peering connection when using standalone etcd, 4001 used for non-clustered etcd to accept change in state.