+.SS "The ``enable\-protocol'' command"
+.
+.PP
+The \fBenable\-protocol\fR command checks for rules related to a
+specified protocol in the system's \fBiptables\fR(8) configuration. If there
+are no rules specifically related to that protocol, then it inserts a
+rule to accept the specified protocol.
+.
+.PP
+More specifically:
+.
+.IP \(bu
+If \fBiptables\fR is not installed or not enabled, this command does
+nothing, assuming that lack of filtering means that the protocol is
+enabled.
+.
+.IP \(bu
+If the \fBINPUT\fR chain has a rule that matches the specified
+protocol, then this command does nothing, assuming that whatever rule
+is installed reflects the system administrator's decisions.
+.
+.IP \(bu
+Otherwise, this command installs a rule that accepts traffic of the
+specified protocol.
+.
+.PP
+This command normally completes successfully, even if it does
+nothing. Only the failure of an attempt to insert a rule normally
+causes it to return an exit code other than 0.
+.
+The following options control the protocol to be enabled:
+.
+.IP "\fB\-\-protocol=\fIprotocol\fR"
+The name of the IP protocol to be enabled, such as \fBgre\fR or
+\fBtcp\fR. The default is \fBgre\fR.
+.
+.IP "\fB\-\-sport=\fIsport\fR"
+.IQ "\fB\-\-dport=\fIdport\fR"
+TCP or UDP source or destination port to match. These are optional
+and allowed only with \fB\-\-protocol=tcp\fR or
+\fB\-\-protocol=udp\fR.
+.