Docker Network moving from the default bridge - docker

Question

I have a bunch of docker containers running on the default bridge network, that need to communicate with each other.
I want to move some of the containers to a separate user defined network so I can specify their IP addresses.
Is there any way to do this without having to take down/replicate all the containers and move them to the other network, or is this the only way?

Answer 1

It's possible to create networks and connect containers while they are live. You may still need to stop/start processes if the process is listening on specific a IP addresses rather than all interfaces (* or :: )
Create a network
docker network create \
--driver=bridge \
--subnet=192.168.38.0/24 \
--gateway=172.16.238.1 \
<NETWORK>
Connect a container
docker network connect \
--ip 192.168.38.14 \
<NETWORK> \
<CONTAINER>
Disconnect from original network
docker network disconnect <OLDNETWORK> <CONTAINER>
Example
Before the containers eth0 is on the default bridge network
→ docker exec $CONTAINER ip ad sh
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
15: eth0#if16: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
link/ether 02:42:ac:11:00:04 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.4/16 brd 172.17.255.255 scope global eth0
valid_lft forever preferred_lft forever
Afterwards, eth1 has been added and no more eth0
→ docker exec $CONTAINER ip ad sh
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
17: eth1#if18: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
link/ether 02:42:c0:a8:26:0e brd ff:ff:ff:ff:ff:ff
inet 192.168.38.14/24 brd 192.168.38.255 scope global eth1
valid_lft forever preferred_lft forever

Answer 2

You also should think about using a docker compose. It will create a network automatically, with its own DNS, allowing the containers to be connected.