diff -ru ppp-2.4.2/pppd/auth.c ppp-2.4.2.sigalrm/pppd/auth.c
--- ppp-2.4.2/pppd/auth.c	2003-06-11 18:56:26.000000000 -0500
+++ ppp-2.4.2.sigalrm/pppd/auth.c	2005-08-13 19:57:25.000000000 -0500
@@ -1053,6 +1053,10 @@
 	itime = MIN(idle.xmit_idle, idle.recv_idle);
 	tlim = idle_time_limit - itime;
     }
+    if (extidle) {
+	itime = time() - reset_time;
+	tlim = idle_time_limit - itime;
+    }
     if (tlim <= 0) {
 	/* link is idle: shut it down. */
 	notice("Terminating connection due to lack of activity.");
diff -ru ppp-2.4.2/pppd/main.c ppp-2.4.2.sigalrm/pppd/main.c
--- ppp-2.4.2/pppd/main.c	2004-01-12 22:00:34.000000000 -0600
+++ ppp-2.4.2.sigalrm/pppd/main.c	2005-08-13 20:23:04.000000000 -0500
@@ -149,6 +149,7 @@
 int got_sigusr2;
 int got_sigterm;
 int got_sighup;
+int got_sigalrm;
 
 static int waiting;
 static sigjmp_buf sigjmp;
@@ -204,6 +205,7 @@
 static void hup __P((int));
 static void term __P((int));
 static void chld __P((int));
+static void alrm __P((int));
 static void toggle_debug __P((int));
 static void open_ccp __P((int));
 static void bad_signal __P((int));
@@ -721,13 +723,13 @@
 
     SIGNAL(SIGUSR1, toggle_debug);	/* Toggle debug flag */
     SIGNAL(SIGUSR2, open_ccp);		/* Reopen CCP */
+    SIGNAL(SIGALRM, alrm);		/* Reset activity timer */ 
 
     /*
      * Install a handler for other signals which would otherwise
      * cause pppd to exit without cleaning up.
      */
     SIGNAL(SIGABRT, bad_signal);
-    SIGNAL(SIGALRM, bad_signal);
     SIGNAL(SIGFPE, bad_signal);
     SIGNAL(SIGILL, bad_signal);
     SIGNAL(SIGPIPE, bad_signal);
@@ -1402,6 +1404,18 @@
 
 
 /*
+ * alrm - Catch SIGALRM signal.
+ * Resets external timeout timer.
+ */
+static void
+alrm(sig)
+    int sig;
+{
+    got_sigalrm = 1;
+    reset_time = time();
+}
+
+/*
  * toggle_debug - Catch SIGUSR1 signal.
  *
  * Toggle debug flag.
diff -ru ppp-2.4.2/pppd/options.c ppp-2.4.2.sigalrm/pppd/options.c
--- ppp-2.4.2/pppd/options.c	2004-01-12 22:02:07.000000000 -0600
+++ ppp-2.4.2.sigalrm/pppd/options.c	2005-08-13 20:13:33.000000000 -0500
@@ -219,6 +219,8 @@
 
     { "demand", o_bool, &demand,
       "Dial on demand", OPT_INITONLY | 1, &persist },
+    { "external-filter", o_bool, &extidle,
+      "Use SIGALRM to wake up demand timer", OPT_INITONLY | 1},
 
     { "--version", o_special_noarg, (void *)showversion,
       "Show version number" },
diff -ru ppp-2.4.2/pppd/pppd.h ppp-2.4.2.sigalrm/pppd/pppd.h
--- ppp-2.4.2/pppd/pppd.h	2003-04-06 19:01:46.000000000 -0500
+++ ppp-2.4.2.sigalrm/pppd/pppd.h	2005-08-13 20:13:46.000000000 -0500
@@ -245,6 +245,7 @@
 extern int      ppp_session_number; /* Session number (eg PPPoE session) */
 
 extern int	listen_time;	/* time to listen first (ms) */
+extern time_t	reset_time;	/* time of last SIGALRM */
 extern struct notifier *pidchange;   /* for notifications of pid changing */
 extern struct notifier *phasechange; /* for notifications of phase changes */
 extern struct notifier *exitnotify;  /* for notification that we're exiting */
@@ -289,6 +290,7 @@
 extern char	remote_name[MAXNAMELEN]; /* Peer's name for authentication */
 extern bool	explicit_remote;/* remote_name specified with remotename opt */
 extern bool	demand;		/* Do dial-on-demand */
+extern bool	extidle;	/* Use external idle/demand filter */
 extern char	*ipparam;	/* Extra parameter for ip up/down scripts */
 extern bool	cryptpap;	/* Others' PAP passwords are encrypted */
 extern int	idle_time_limit;/* Shut down link if idle for this long */