How to assign static public IP to docker container

This should now be possible with docker 1.10 and the new docker run --ip option that you now see in docker network connect.

If specified, the container's IP address(es) is reapplied when a stopped container is restarted. If the IP address is no longer available, the container fails to start.

One way to guarantee that the IP address is available is to specify an --ip-range when creating the network, and choose the static IP address(es) from outside that range. This ensures that the IP address is not given to another container while this container is not on the network.

$ docker network create --subnet 172.20.0.0/16 --ip-range 172.20.240.0/20 multi-host-network

$ docker network connect --ip 172.20.128.2 multi-host-network container2

See also Jessie Frazelle's blog post "IPs for all the Things", and pull request docker/docker#19001.

With currently released versions of Docker this isn't possible (without a lot of manual work behind Docker's back), although it is seldom necessary.

Docker exposes network services in containers through the use of port mappings, and port mappings can bind to specific ip addresses on your host. So if you want to have one web server at 192.168.10.10 and another webserver at 192.168.10.20, first make sure this addresses are available on your host:

ip addr add 192.168.10.10/24 dev eth0
ip addr add 192.168.10.20/24 dev eth0

Then start the first container:

docker run -p 192.168.10.10:80:80 mywebserver

And finally start the second container:

docker run -p 192.168.10.20:80:80 mywebserver

In the above commands, the -p option is used to bind the port mapping to a particular ip address. Now you have two containers offering a service on the same port (port 80) but on different ip addresses.

Since this question pops up on popular searches (docker assign ip container etc), the (currently) accepted answer is obsolete, and the correct one of @VonC is somewhat inconclusive (including discussion) let us summarize with an example of how it can be done and what the result is:

docker run -d nginx:latest  #--> container with id be46...
docker network create --subnet 10.30.0.0/24 --ip-range 10.30.0.0/24 multi-host-network
docker network connect --ip 10.30.0.4 multi-host-network be46

now the container has 10.30.0.4/24 attached; you can ping 10.30.0.4 from the host on which the commands were run. After docker stop be46 ping's don't work anymore, and after you docker start be46 pings succeed again. On the host, the following route is created:

10.30.0.0/24 dev br-b74e7b452f23 proto kernel scope link src 10.30.0.1

(so the host assumes 10.30.0.1).

Note: this completes the task of "assigning given IP to a container", but it is unclear to me for now if you could do that in the "docker swarm" context, and achieve the same level of redundancy we have there (with the assignment of ports to services).