-\fBtun_id\fR requires use of one of two Nicira extensions to OpenFlow:
-.RS
-.IP "NXM (Nicira Extended Match)"
-This extension fully supports \fBtun_id\fR.
-.IP "Tunnel ID from Cookie"
-This extension supports \fBtun_id\fR with three caveats: the top 32 bits
-of the \fBcookie\fR (see below) are used for \fItunnel-id\fR and thus
-unavailable for other use, specifying \fBtun_id\fR on
-\fBdump\-flows\fR or \fBdump\-aggregate\fR has no effect, and
-\fImask\fR is not supported.
-.RE
-.IP
-When \fBtun_id\fR is specified, \fBovs\-ofctl\fR will automatically
-attempt to negotiate use of one of these extensions. It will use the
-``tunnel ID from cookie'' extension if neither caveat applies and NXM
-otherwise. If the switch does not support the needed extension, then
-\fBovs\-ofctl\fR will report a fatal error.
+In an attempt to be compatible with more switches, \fBovs\-ofctl\fR will
+prefer to use the ``tunnel ID from cookie'' Nicira extension to NXM.
+The use of this extension comes with three caveats: the top 32 bits of
+the \fBcookie\fR (see below) are used for \fItunnel-id\fR and thus
+unavailable for other use, specifying \fBtun_id\fR on \fBdump\-flows\fR
+or \fBdump\-aggregate\fR has no effect, and \fImask\fR is not supported.
+If any of these caveats apply, \fBovs-ofctl\fR will use NXM.
+.