Container network drivers


The Docker Engine supports many different network drivers.

The built-in drivers include:

  • bridge (default)

  • none

  • host

  • container

The driver is selected with docker run --net ....

The different drivers are explained with more details on the following slides.

The default bridge

  • By default, the container gets a virtual eth0 interface.
    (In addition to its own private lo loopback interface.)

  • That interface is provided by a veth pair.

  • It is connected to the Docker bridge.
    (Named docker0 by default; configurable with --bridge.)

  • Addresses are allocated on a private, internal subnet.
    (Docker uses by default; configurable with --bip.)

  • Outbound traffic goes through an iptables MASQUERADE rule.

  • Inbound traffic goes through an iptables DNAT rule.

  • The container can have its own routes, iptables rules, etc.

The null driver

  • Container is started with docker run --net none ...

  • It only gets the lo loopback interface. No eth0.

  • It can't send or receive network traffic.

  • Useful for isolated/untrusted workloads.

The host driver

  • Container is started with docker run --net host ...

  • It sees (and can access) the network interfaces of the host.

  • It can bind any address, any port (for ill and for good).

  • Network traffic doesn't have to go through NAT, bridge, or veth.

  • Performance = native!

Use cases:

  • Performance sensitive applications (VOIP, gaming, streaming...)

  • Peer discovery (e.g. Erlang port mapper, Raft, Serf...)

The container driver

  • Container is started with docker run --net container:id ...

  • It re-uses the network stack of another container.

  • It shares with this other container the same interfaces, IP address(es), routes, iptables rules, etc.

  • Those containers can communicate over their lo interface.
    (i.e. one can bind to and the others can connect to it.)