What is the relation between docker0 and eth0?

Question

I know by default docker creates a virtual bridge docker0, and all container network are linked to docker0.

Answer 1

You can detect the relation by network interface iflink from a container and ifindex on the host machine.

Get iflink from a container:

$ docker exec ID cat /sys/class/net/eth0/iflink

17253

Then find this ifindex among interfaces on the host machine:

$ grep -l 17253 /sys/class/net/veth*/ifindex

/sys/class/net/veth02455a1/ifindex