Container network interface

A container needs at least one network interface to communicate with other containers or endpoints.

In Kubernetes, the container network is extended across the cluster and governs how the network traffic happens across the nodes in the cluster. From the application developer point of view, all of the containers in a Kubernetes cluster are on a flat subnet.

When a container is started, a logical network interface is provided inside the container through one end of a veth pair in the container's network namespace. The other end of the veth pair is presented in the default network namespace on the worker node. The veth pair end on the node can be presented either as a logical interface or an interface on a layer-2 bridge depending on the underlying networking technology.

Example: eth0 connected to a logical network interface on a node's default network namespace

Example: eth0 connected to a bridge interface on a node's default network namespace and bridge with an uplink