Docker 1.10 container's IP in LAN

Question

Since Docker 1.10 (and libnetwork update) we can manually give an IP to a container inside a user-defined network, and that's cool!

I want to give a container an IP address in my LAN (like we can do with Virtual Machines in "bridge" mode). My LAN is 192.168.1.0/24, all my computers have IP addresses inside it. And I want my containers having IPs in this range, in order to reach them from anywhere in my LAN (without NAT/PAT/etc...).

I obviously read Jessie Frazelle's blog post and a lot of others post here and everywhere like :

• How to set a docker container's iP?
• How to assign specific IP to container and make that accessible outside of VM host?

and so much more, but nothing came out; my containers still have IP addresses "inside" my docker host, and are not reachable for others computers on my LAN.

Reading Jessie Frazelle's blog post, I thought (since she uses public IP) we can do what I want to do?

Edit: Indeed, if I do something like :

network create --subnet 192.168.1.0/24 --gateway 192.168.1.1 homenet
docker run --rm -it --net homenet --ip 192.168.1.100 nginx

The new interface on the docker host (br-[a-z0-9]+) take the '--gateway' IP, which is my router IP. And the same IP on two computers on the network... BOOM

Thanks in advance.

Answer 1

EDIT : This solution is now useless. Since version 1.12, Docker provides two network drivers : macvlan and ipvlan. They allow assigning static IP from the LAN network. See the answer below.

---

After looking for people who have the same problem, we went to a workaround :

Sum up :

• (V)LAN is 192.168.1.0/24
• Default Gateway (= router) is 192.168.1.1
• Multiple Docker Hosts
• Note : We have two NIC : eth0 and eth1 (which is dedicated to Docker)

What do we want :

We want to have containers with ip in the 192.168.1.0/24 network (like computers) without any NAT/PAT/translation/port-forwarding/etc...

Problem

When doing this :

network create --subnet 192.168.1.0/24 --gateway 192.168.1.1 homenet 

we are able to give containers the IP we want to, but the bridge created by docker (br-[a-z0-9]+) will have the IP 192.168.1.1, which is our router.

Solution

1. Setup the Docker Network

Use the DefaultGatewayIPv4 parameter :

docker network create --subnet 192.168.1.0/24 --aux-address "DefaultGatewayIPv4=192.168.1.1" homenet 

By default, Docker will give to the bridge interface (br-[a-z0-9]+) the first IP, which might be already taken by another machine. The solution is to use the --gateway parameter to tell docker to assign a arbitrary IP (which is available) :

docker network create --subnet 192.168.1.0/24 --aux-address "DefaultGatewayIPv4=192.168.1.1" --gateway=192.168.1.200 homenet 

We can specify the bridge name by adding -o com.docker.network.bridge.name=br-home-net to the previous command.

2. Bridge the bridge !

Now we have a bridge (br-[a-z0-9]+) created by Docker. We need to bridge it to a physical interface (in my case I have to NIC, so I'm using eth1 for that):

brctl addif br-home-net eth1 

3. Delete the bridge IP

We can now delete the IP address from the bridge, since we don't need one :

ip a del 192.168.1.200/24 dev br-home-net 

The IP 192.168.1.200 can be used as bridge on multiple docker host, since we don't use it, and we remove it.

Answer 2

Docker now supports Macvlan and IPvlan network drivers. The Docker documentation for both network drivers can be found here.

With both drivers you can implement your desired scenario (configure a container to behave like a virtual machine in bridge mode):

• Macvlan: Allows a single physical network interface (master device) to have an arbitrary number of slave devices, each with it's own MAC adresses.

  Requires Linux kernel v3.9–3.19 or 4.0+.

• IPvlan: Allows you to create an arbitrary number of slave devices for your master device which all share the same MAC address.

  Requires Linux kernel v4.2+ (support for earlier kernels exists but is buggy).

  See the kernel.org IPVLAN Driver HOWTO for further information.

Container connectivity is achieved by putting one of the slave devices into the network namespace of the container to be configured. The master devices remains on the host operating system (default namespace).

As a rule of thumb you should use the IPvlan driver if the Linux host that is connected to the external switch / router has a policy configured that allows only one MAC per port. That's often the case in VMWare ESXi environments!

Another important thing to remember (Macvlan and IPvlan): Traffic to and from the master device cannot be sent to and from slave devices. If you need to enable master to slave communication see section "Communication with the host (default-ns)" in the "IPVLAN – The beginning" paper published by one of the IPvlan authors (Mahesh Bandewar).

Answer 3

Use the official Docker driver:

As of Docker v1.12.0-rc2, the new MACVLAN driver is now available in an official Docker release:

• MacVlan driver is out of experimental #23524

These new drivers have been well documented by the author(s), with usage examples.

End of the day it should provide similar functionality, be easier to setup, and with fewer bugs / other quirks.

Seeing Containers on the Docker host:

Only caveat with the new official macvlan driver is that the docker host machine cannot see / communicate with its own containers. Which might be desirable or not, depending on your specific situation.

This issue can be worked-around if you have more than 1 NIC on your docker host machine. And both NICs are connected to your LAN. Then can either A) dedicate 1 of your docker hosts's 2 nics to be for docker exclusively. And be using the remaining nic for the host to access the LAN.

Or B) by adding specific routes to only those containers you need to access via the 2nd NIC. For example:

sudo route add -host $container_ip gw $lan_router_ip $if_device_nic2

Method A) is useful if you want to access all your containers from the docker host and you have multiple hardwired links.

Wheras method B) is useful if you only require access to a few specific containers from the docker host. Or if your 2nd NIC is a wifi card and would be much slower for handling all of your LAN traffic. For example on a laptop computer.

Installation:

If cannot see the pre-release -rc2 candidate on ubuntu 16.04, temporarily add or modify this line to your /etc/apt/sources.list to say:

deb https://apt.dockerproject.org/repo ubuntu-xenial testing

instead of main (which is stable releases).