The previous recipe showed how we can use OVS in place of a standard Linux bridge. This, by itself, isn't very interesting since it doesn't do a lot more than a standard Linux bridge can. What may be interesting is using some of the more advanced features of OVS in conjunction with your Docker containers. For instance, once the OVS bridges are created, it's rather trivial to provision GRE tunnels between two distinct Docker hosts. This would allow any containers connected to either Docker host to talk directly to each other. In this recipe, we'll discuss the configuration required to connect two Docker hosts using an OVS provided GRE tunnel.
Note
Again, this recipe is for the purpose of example only. This behavior is already supported by Docker's user-defined overlay network type. If for some reason you need to use GRE rather than VXLAN, this might be a suitable alternative. As always, make sure that you use any Docker native networking constructs...