Let's create two containers, running the web tier and the database tier:

APACHE=$(docker run -d apache /usr/sbin/httpd -D FOREGROUND)
MYSQL=$(docker run -d mysql /usr/sbin/mysqld_safe)

Now, bring superpowers to the web tier:

pipework br1 $APACHE 192.168.1.1/24

This will:

• create a bridge named br1 in the docker host;
• add an interface named eth1 to the $APACHE container;
• assign IP address 192.168.1.1 to this interface,
• connect said interface to br1.

Now (drum roll), let's do this:

pipework br1 $MYSQL 192.168.1.2/24

This will:

• not create a bridge named br1, since it already exists;
• add an interface named eth1 to the $MYSQL container;
• assign IP address 192.168.1.2 to this interface,
• connect said interface to br1.

Now, both containers can ping each other on the 192.168.1.0/24 subnet.

Pipework can resolve Docker containers names. If the container ID that you gave to Pipework cannot be found, Pipework will try to resolve it with docker inspect. This makes it even simpler to use:

docker run -name web1 -d apache
pipework br1 web1 192.168.12.23/24

Want to connect to those containers using their private addresses? Easy:

ip addr add 192.168.1.254/24 dev br1

Voilà!

pipework br1 -i eth2 ...

Note:: for infiniband IPoIB interfaces, the default interface name is ib0 and not eth1.

The IP addresses given to pipework are directly passed to the ip addr tool; so you can append a subnet size using traditional CIDR notation.

I.e.:

pipework br1 $CONTAINERID 192.168.4.25/20

Don't forget that all containers should use the same subnet size; pipework is not clever enough to use your specified subnet size for the first container, and retain it to use it for the other containers.

If you want outbound traffic (i.e. when the containers connects to the outside world) to go through the interface managed by Pipework, you need to change the default route of the container.

This can be useful in some usecases, like traffic shaping, or if you want the container to use a specific outbound IP address.

This can be automated by Pipework, by adding the gateway address after the IP address and subnet mask:

pipework br1 $CONTAINERID 192.168.4.25/[email protected]

Let's pretend that you want to run two Hipache instances, listening on real interfaces eth2 and eth3, using specific (public) IP addresses. Easy!

pipework eth2 $(docker run -d hipache /usr/sbin/hipache) 50.19.169.157/24
pipework eth3 $(docker run -d hipache /usr/sbin/hipache) 107.22.140.5/24

Note that this will use macvlan subinterfaces, so you can actually put multiple containers on the same physical interface.

If you use macvlan interfaces as shown in the previous paragraph, you will notice that the host will not be able to reach the containers over their macvlan interfaces. This is because traffic going in and out of macvlan interfaces is segregated from the "root" interface.

If you want to enable that kind of communication, no problem: just create a macvlan interface in your host, and move the IP address from the "normal" interface to the macvlan interface.

For instance, on a machine where eth0 is the main interface, and has address 10.1.1.123/24, with gateway 10.1.1.254, you would do this:

ip addr del 10.1.1.123/24 dev eth0
ip link add link eth0 dev eth0m type macvlan mode bridge
ip link set eth0m up
ip addr add 10.1.1.123/24 dev eth0m
route add default gw 10.1.1.254

Then, you would start a container and assign it a macvlan interface the usual way:

CID=$(docker run -d ...)
pipework eth0 $CID 10.1.1.234/[email protected]

Sometimes, you want the extra network interface to be up and running before starting your service. A dirty (and unreliable) solution would be to add a sleep command before starting your service; but that could break in "interesting" ways if the server happens to be a bit slower at one point.

There is a better option: add the pipework script to your Docker image, and before starting the service, call pipework --wait. It will wait until the eth1 interface is present and in UP operational state, then exit gracefully.

If you meed to wait on an interface other than eth1, pass the -i flag like this:

pipework --wait -i ib0

If for some reason you want to set the IP address from within the container, you can use 0/0 as the IP address. The interface will be created, connected to the network, and assigned to the container, but without configuring an IP address:

pipework br1 $CONTAINERID 0/0

You can use DHCP to obtain the IP address of the new interface. Just specify dhcp instead of an IP address; for instance:

pipework eth1 $CONTAINERID dhcp

The value of $CONTAINERID will be provided to the DHCP client to use as the hostname in the DHCP request. Depending on the configuration of your network's DHCP server, this may enable other machines on the network to access the container using the $CONTAINERID as a hostname; therefore, specifying $CONTAINERID as a container name rather than a container id may be more appropriate in this use-case.

You need three things for this to work correctly:

• obviously, a DHCP server (in the example above, a DHCP server should be listening on the network to which we are connected on eth1);
• a DHCP client (either udhcpc, dhclient or dhcpcp) must be installed on your Docker host (you don't have to install it in your containers, but it must be present on the host);
• the underlying network must support bridged frames.

The last item might be particularly relevant if you are trying to bridge your containers with a WPA-protected WiFi network. I'm not 100% sure about this, but I think that the WiFi access point will drop frames originating from unknown MAC addresses; meaning that you have to go through extra hoops if you want it to work properly.

It works fine on plain old wired Ethernet, though.

If you need to specify the MAC address to be used (either by the macvlan subinterface, or the veth interface), no problem. Just add it as the command-line, as the last argument:

pipework eth0 $(docker run -d haproxy) 192.168.1.2/24 26:2e:71:98:60:8f

If you want to attach a container to the Open vSwitch bridge, no problem.

ovs-vsctl list-br
ovsbr0
pipework ovsbr0 $(docker run -d mysql /usr/sbin/mysqld_safe) 192.168.1.2/24

If the ovs bridge doesn't exist, it will be automatically created

Passing an IPoIB interface to a container is supported. The IPoIB device is created as a virtual device. It's similar to a macvlan but for IPoIB devices. Also supported are partition keys.

The following will attach a container to ib0

pipework ib0 $CONTAINERID 10.10.10.10/24

The following will do the same but connect it to ib0 with pkey 8001

pipework ib0 $CONTAINERID 10.10.10.10/24 @8001

When a container is terminated (the last process of the net namespace exits), the network interfaces are garbage collected. The interface in the container is automatically destroyed, and the interface in the docker host (part of the bridge) is then destroyed as well.