Docker Cookbook

3.7 Using pipework to Understand Container Networking | 87

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for network namespaces. Doing so, you can list the existing network namespaces.
Next, you see that the namespace ID of your container is the container ID:
$ cd /var/run
$ sudo ln -s /var/run/docker/netns netns
$ sudo ip netns
c785553b22a1
$ NID=$(sudo ip netns)
Now, let’s put the 
bar
veth in the container namespace by using 
ip link set netns
and use 
ip netns exec
to give it a name and a MAC address inside this namespace:
$ sudo ip link set bar netns $NID
$ sudo ip netns exec $NID ip link set dev bar name eth1
$ sudo ip netns exec $NID ip link set eth1 address 12:34:56:78:9a:bc
$ sudo ip netns exec $NID ip link set eth1 up
The final thing to do is to assign an IP address to 
eth1
of the container and define a
default route so that the container can reach the Docker host and beyond:
$ sudo ip netns exec $NID ip addr add 192.168.1.1/24 dev eth1
$ sudo ip netns exec $NID ip route add default via 192.168.1.254
That’s it. At this stage, your container should have the exact same networking stack as
the one built with pipework earlier with a single command.
Remember that if you want to reach outside your container, you
need to add the IP NAT masquerading rule:
$ sudo iptables -t nat -A POSTROUTING -s 192.168.0.0/24
-j MASQUERADE
See Also
•
pipework’s
extensive 
README
covers multiple scenarios
• How Docker 
networks
 containers
•
ip netns
 man 
page
• Introduction to Linux nework 
namespace
3.8 Setting Up a Custom Bridge for Docker
Problem
You would like to set up your own bridge for Docker to use instead of using the
default.