Docker Cookbook

3.10 Building a GRE Tunnel Between Docker Hosts | 91

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case this technique, you are going to bring up two Docker hosts and set up the net‐
work configuration that you can see in 
Figure 3-2
.
Host 1 has IP address 
192.168.33.11
. We will give the 
docker0
bridge IP address
172.17.0.1
and create a GRE tunnel endpoint with IP address 
172.17.0.2
. Docker
will give containers addresses in the 
172.17.0.0/17
network.
Host 2 has IP address 
192.168.33.12
. We will give the 
docker0
bridge IP address
172.17.128.1
and create a GRE tunnel endpoint with IP address 
171.17.128.2
.
Docker will give containers addresses in the 
172.17.128.0/17
network.
Splitting a 
/16
network in two 
/17
networks and assigning each subnet to the two
different hosts ensures that containers will not get conflicting IP addresses.
Figure 3-2. Network diagram of a two-hosts GRE tunnel overlay
You can start this configuration with a 
Vagrantfile
. Each host has the latest stable ver‐
sion of Docker and two network interfaces: one NAT interface that gives outbound
connectivity and one interface on a private network.
The first thing to do to avoid any issues is to stop the Docker engine and remove that
docker0
bridge that was started during the Docker provisioning step. You will need to
do this on all your hosts:
$ sudo su
# service docker stop
# ip link set docker0 down
# ip link del docker0
Now you can create a GRE tunnel between the two hosts. You do not need Open
vSwitch for this; you can just use the 
ip
tool. If you used the Vagrantfile mentioned
earlier, on your first host with IP 
192.168.33.11
do the following: