-To use ovs-openflowd in userspace mode, specify a datapath name that
-begins with "netdev:", and specify --ports with the names of the ports
-that should be included in the datapath as argument. For example:
+On Linux, when a physical interface is in use by the userspace
+datapath, packets received on the interface still also pass into the
+kernel TCP/IP stack. This can cause surprising and incorrect
+behavior. You can use "iptables" to avoid this behavior, by using it
+to drop received packets. For example, to drop packets received on
+eth0: