This option is most useful for debugging. It reduces switching
performance, so it should not be used in production.
+.TP
+\fB--max-idle=\fIsecs\fR|\fBpermanent\fR
+Sets \fIsecs\fR as the number of seconds that a flow set up by the
+controller will remain in the switch's flow table without any matching
+packets being seen. If \fBpermanent\fR is specified, which is not
+recommended, flows will never expire. The default is 60 seconds.
+
+This option affects only flows set up by the OpenFlow controller. In
+some configurations, the OpenFlow secure channel can set up some flows
+on its own. To set the idle time for those flows, pass
+\fB--max-idle\fR to \fBsecchan\fR(8).
+
+This option has no effect when \fB-n\fR (or \fB--noflow\fR) is in use
+(because the controller does not set up flows in that case).
+
.TP
.BR \-H ", " \-\^\-hub
By default, the controller acts as an L2 MAC-learning switch. This