+.B netmask \fImask
+Set the IPV4 network mask on the PPP interface to the given
+\fImask\fR, which can be given in dotted-quad notation or as a single
+hexadecimal number preceded by 0x. This option is not normally
+needed because the PPP interface is a point-to-point connection, but
+in some specialized circumstances it can be useful.
+.TP