You can see for instance docker0
described in this article:
The docker0 bridge is virtual interface created by docker, it randomly chooses an address and subnet from the private range defined by RFC 1918 that are not in use on the host machine, and assigns it to docker0
.
All the docker containers will be connected to the docker0 bridge by default, the docker containers connnected to the docker0
bridge could use the iptables NAT rules created by docker to communicate with the outside world.

By default Docker will attach all containers to the docker0 bridge, so you do not need to specify any additional flag with docker run command to connect the docker containers to the docker0
bridge, unless the DOCKER_OPTS
in docker configuration file explicitly specifies to use the other network than docker0
bridge, in this case you could use –net=bridge
with docker run command to connect the containers to the docker0
bridge.
See also "What is the relation between docker0
and eth0
?"