Docker Cookbook

3.12 Running a Weave Network on AWS | 97

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See Also
•
Weave Getting Started Guides
3.13 Deploying flannel Overlay Between Docker Hosts
Contributed by Eugene Yakubovich
Problem
You want containers on different hosts to communicate with each other without port
mapping.
Solution
Use 
flannel
to create an overlay network for containers. Each container will be
assigned an IP that can be reachable from other hosts. Start by bringing up two vir‐
tual machines from a Vagrantfile:
$ git clone https://github.com/how2dock/docbook.git
$ cd ch03/flannel
$ vagrant up
This defines two virtual machines installed with Docker: 
etcd
and 
flannel
. The
“master” will run a key-value store (
etcd
) that 
flannel
uses for coordination.
Next, 
vagrant ssh master
and start 
etcd
in the background:
$ cd /opt/coreos/etcd-v2.0.13-linux-amd64
$ nohup ./etcd --listen-client-urls=http://0.0.0.0:2379 \
--advertise-client-urls=http://192.168.33.10:2379 &
Before starting the 
flannel
daemon, write the overlay network configuration into
etcd
. Be sure to pick a subnet range that does not conflict with other IP addresses:
$ ./etcdctl set /coreos.com/network/config '{ "Network": "10.100.0.0/16" }'
Now start the 
flannel
daemon. Notice that the 
--iface
option specifies the IP of the
private network given in the Vagrantfile. 
flannel
will forward encapsulated packets
over this interface:
$ cd /opt/coreos/flannel-0.5.1
$ sudo ./flanneld --iface=192.168.33.10 --ip-masq &
$ sudo ./mk-docker-opts.sh -c -d /etc/default/docker
flannel
will acquire a lease for a 
/24
subnet to be assigned to the 
docker0
bridge.
The acquired subnet will be written out to the 
/run/flannel/subnet.env
file. The