---
title: Using Weave Net via Docker Networking
layout: default
---

# Weave Plugin

New in Docker version 1.9 is a plugin mechanism to add different
network providers.

To install, download the `weave` script as per the [readme][].

The Weave Net plugin runs automatically when you `weave launch`.  You
must still tell the weave peers to connect to one another, either via
`weave launch` or `weave connect`.

Note that the plugin container (`weaveplugin`) is run with
`--restart=always`, so that it is there after a restart or reboot. If
you remove this container (e.g. using `weave reset`) before removing
all endpoints created using `--net=weave`, Docker can
[hang](https://github.com/docker/libnetwork/issues/813).

## Starting a container

    $ docker run --net=weave -ti ubuntu

## Using WeaveDNS for Service Discovery

You need to pass the additional arguments `--dns` and `-dns-search`,
for which we provide a helper in the weave script:

    $ docker run --net=weave -h foo.weave.local $(weave dns-args) -tdi ubuntu
    $ docker run --net=weave -h bar.weave.local $(weave dns-args) -ti ubuntu
    # ping foo

For more details see the [Weave Service Discovery documentation][service-discovery].

## Under the hood

The Weave Net plugin actually provides *two* network drivers to Docker
- one named `weavemesh` that can operate without a [cluster
store](#cluster-store) (like Docker's overlay driver) and one named
`weave` that can only work with one.

### `weavemesh` driver

* Weave handles all co-ordination between hosts (referred to by Docker as a "local scope" driver)
* Supports only a single network (we create one named `weave` for you automatically)
* Uses Weave's partition tolerant IPAM

If you do create additional networks using the `weavemesh` driver,
containers attached to them will be able to communicate with
containers attached to `weave`; there is no isolation between those
networks.

### `weave` driver

* This runs in what Docker call "global scope"; requires a cluster store
* Supports multiple networks (these must be created with `docker network create --driver weave ...`)
* Used with Docker's cluster store based IPAM

There's no specific documentation from Docker on using a cluster
store, but the first part of [Getting Started with Docker Multi-host Networking][docker-net]
should point the way.

Note that in the case of multiple networks using the `weave` driver, all containers are
on the same virtual network but Docker allocates their addresses on
different subnets so they cannot talk to each other directly.

## Plugin command-line arguments

If you want to give some arguments to the plugin independently, don't
use `weave launch`; instead run:

    $ weave launch-router [other peers]
    $ weave launch-plugin [plugin arguments]

The plugin command-line arguments are:

 * `--log-level=debug|info|warning|error`, which tells the plugin
   how much information to emit for debugging.
 * `--mesh-network-name=<name>`: set it to blank to disable creation
   of a default network, or a name of your own choice.
 * `--no-multicast-route`: stop weave adding a static IP route for
   multicast traffic on its interface

## Restarting

We start the plugin with a restart policy, because Docker attempts to
recreate networks on startup.  If it isn't started automatically by
Docker with a restart policy, it's not possible to start it manually
because Docker is blocked.

Specifically, we use the policy `on-failure:3`, so Docker will give up
after three attempts if something just isn't working.

[readme]: https://github.com/weaveworks/weave/blob/master/README.md#installation
[service-discovery]: weavedns.html
[docker-net]: https://github.com/docker/docker/blob/master/docs/userguide/networking/get-started-overlay.md