A single Weave network can host multiple, isolated applications where each application’s containers are able to communicate with each other, but not with the containers of other applications.

To isolate applications, you can make use of isolation-through-subnets technique. This common strategy is an example of how with Weave Net many of your on metal techniques can still be used to deploy applications to a container network.

To begin isolating an application (or parts of an application),
configure Weave Net’s IP allocator to manage multiple subnets.

Using the netcat example, configure multiple subsets:

host1$ weave launch --ipalloc-range --ipalloc-default-subnet
host1$ eval $(weave env)
host2$ weave launch --ipalloc-range --ipalloc-default-subnet $HOST1
host2$ eval $(weave env)

This delegates the entire subnet to Weave Net, and instructs it to allocate from within that, if a specific subnet is not specified.

Next, launch the two netcat containers onto the default subnet:

host1$ docker run --name a1 -ti weaveworks/ubuntu
host2$ docker run --name a2 -ti weaveworks/ubuntu

And then to test the isolation, launch a few more containers onto a different subnet:

host1$ docker run -e WEAVE_CIDR=net: --name b1 -ti weaveworks/ubuntu
host2$ docker run -e WEAVE_CIDR=net: --name b2 -ti weaveworks/ubuntu

Ping each container to confirm that they can talk to each other, but not to the containers of our first subnet:

root@b1:/# ping -c 1 -q b2
PING b2.weave.local ( 56(84) bytes of data.
--- b2.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.338/1.338/1.338/0.000 ms

root@b1:/# ping -c 1 -q a1
PING a1.weave.local ( 56(84) bytes of data.
--- a1.weave.local ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

root@b1:/# ping -c 1 -q a2
PING a2.weave.local ( 56(84) bytes of data.
--- a2.weave.local ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

If required, a container can also be attached to multiple subnets when it is started using:

host1$ docker run -e WEAVE_CIDR="net:default net:" -ti weaveworks/ubuntu

net:default is used to request the allocation of an address from the default subnet in addition to one from an explicitly specified range.

Important: Containers must be prevented from capturing and injecting raw network packets - this can be accomplished by starting them with the --cap-drop net_raw option.

Note: By default docker permits communication between containers on the same host, via their docker-assigned IP addresses. For complete isolation between application containers, that feature needs to be disabled by setting --icc=false in the docker daemon configuration.

See Also