Assign LAN IP address to Docker container different from host's IP address

Question

Am not well versed with Unix networking, adding virtual interfaces etc, trying to learn it now. We are trying to dockerize our application.
My requirement is : To assign

Answer 1

My current preferred approach with this is to use either the macvlan or ipvlan Docker network driver. I prefer macvlan as each container can have its own MAC address but some things like VMware don’t like having multiple Mac addresses for a single virtualized nic and won’t route traffic properly.

Setup is pretty straight forward. First you need to determine a few things.

• Subnet of your main network. Using 10.0.0.0/24 for this example
• Gateway of your network. Using 10.0.0.1 for the example
• IP range to use for allocating the ips from (you can statically assign ips outside this range when doing a Docker run if need be). For this example I will use 10.0.0.128/25. You will need a chunk of ips to let Docker manage so you will need to ensure these ips are not in use on your network.
• The name of the device you want to use for the traffic. For the example I will use eth0
• The name of the new Docker network you are going to create. Using “my net” for the example.

Next you create a new Docker network like so:

docker network create -d macvlan —-subnet 10.0.0.0/24 --ip-range 10.0.0.128/25 —-gateway 10.0.0.1 -o parent=eth0 mynet

Now when you start containers use

docker run —-network mynet .....

For more information see the docker docs: https://docs.docker.com/engine/userguide/networking/get-started-macvlan

One caveat to this approach is that macvlan/ipvlan dont seem to work very well with Docker for Mac. The HyperKit vm it creates is a bit of a black box. The macvlan/ipvlan approach requires a more controlled network that Docker for Mac doesn't give you. If you are trying to do this with Docker for Mac then I would suggest setting up a Docker Machine. The docs for how to do that are here: https://docs.docker.com/machine/get-started/.

In this scenario, unless you like setting up routing rules on your Mac, you should have the docker machine use a bridged interface that the macvlan/ipvlan network can then be attached to. In my experience the need for a second NIC that is NAT'ed through the MacOS host is unnecessary but you may find something otherwise.