GRE Tunnels with OpenvSwitch

http://blog.scottlowe.org/2013/05/07/using-gre-tunnels-with-open-vswitch/

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/4/html/Installation_and_Configuration_Guide/Configuring_Open_vSwitch_tunnels.html

http://vlabs.cfapps.io/openvswitch/vlans_gre.html

http://networkstatic.net/configuring-vxlan-and-gre-tunnels-on-openvswitch/

http://networkstatic.net/open-vswitch-gre-tunnel-configuration/