+.B /etc/ppp/ip-up
+A program or script which is executed when the link is available for
+sending and receiving IP packets (that is, IPCP has come up). It is
+executed with the parameters
+.IP
+\fIinterface-name tty-device speed local-IP-address
+remote-IP-address\fR
+.IP
+and with its standard input,
+output and error streams redirected to \fB/dev/null\fR.
+.IP
+This program or script is executed with the same real and effective
+user-ID as \fIpppd\fR, that is, at least the effective user-ID and
+possibly the real user-ID will be \fBroot\fR. This is so that it can
+be used to manipulate routes, run privileged daemons (e.g.
+\fBsendmail\fR), etc. Be careful that the contents of the
+/etc/ppp/ip-up and /etc/ppp/ip-down scripts do not compromise your
+system's security.
+.TP
+.B /etc/ppp/ip-down
+A program or script which is executed when the link is no longer
+available for sending and receiving IP packets. This script can be
+used for undoing the effects of the /etc/ppp/ip-up script. It is
+invoked with the same parameters as the ip-up script, and the same
+security considerations apply, since it is executed with the same
+effective and real user-IDs as \fIpppd\fR.
+.TP