+* The Open vSwitch startup script automatically adds a firewall rule
+to allow GRE traffic. This rule is needed for the XenServer feature
+called "Cross-Host Internal Networks" (CHIN) that uses GRE. If a user
+configures tunnels other than GRE (ex: VXLAN, LISP), they will have
+to either manually add a iptables firewall rule to allow the tunnel traffic
+or add it through a startup script (Please refer to the "enable-protocol"
+command in the ovs-ctl(8) manpage).
+