every time when i start a container with docker it gets a different IP

Question

How do I fix a static IP for a container ?

First I start a container and inspect it, it says

"NetworkSettings": {
    "IPAddress": "XX.XX.206.98",
    "IPPrefixLen": 27,
    "Gateway": "XX.XX.206.105",
    "Bridge": "public",
    "PortMapping": null,
    "Ports": {}
},

then I stop it, and restart, it like

"NetworkSettings": {
    "IPAddress": "XX.XX.206.99",
    "IPPrefixLen": 27,
    "Gateway": "XX.XX.206.105",
    "Bridge": "public",
    "PortMapping": null,
    "Ports": {}
},

As you can see, it changed. I just created a bridge named public, and start docker with -b=public added. How can I set a static IP for a container?

Answer 1

FROM DOCKER 1.10 ON

# create a new bridge network with your subnet and gateway for your ip block
$ docker network create --subnet 203.0.113.0/24 --gateway 203.0.113.254 iptastic

# run a nginx container with a specific ip in that block
$ docker run --rm -it --net iptastic --ip 203.0.113.2 nginx

# curl the ip from any other place (assuming this is a public ip block duh)
$ curl 203.0.113.2

UPDATE

Now the only way to obtain a static IP is through two scripts: pipework or ovs-docker

There is a strong direction towards using Open vSwitch as the "battery included" version of multi hosted docker containers.

Keep an eye on socketplane.

---

This behavior is by design.

There is a very interesting discussion for changing it in future releases.

Up to now the only way you can do it is falling back to linux containers:

docker run \
-n=false \
-lxc-conf="lxc.network.type = veth" \
-lxc-conf="lxc.network.ipv4 = 172.16.42.20/24" \
-lxc-conf="lxc.network.ipv4.gateway = 172.16.42.1" \
-lxc-conf="lxc.network.link = docker0" \
-lxc-conf="lxc.network.name = eth0" \
-lxc-conf="lxc.network.flags = up" \
-i -t my_image:my_tag /bin/bash

So the -n=false disables the automatic docker networking and all the -lxc-conf options are to actually define the virtual network according to your needs.