diff --git a/usr.sbin/rtsold/if.c b/usr.sbin/rtsold/if.c
index 99a1b0ee0126..23e4e6fa02b3 100644
--- a/usr.sbin/rtsold/if.c
+++ b/usr.sbin/rtsold/if.c
@@ -300,6 +300,22 @@ getinet6sysctl(int code)
 		return value;
 }
 
+int
+setinet6sysctl(int code, int newval)
+{
+	int mib[] = { CTL_NET, PF_INET6, IPPROTO_IPV6, 0 };
+	int value;
+	size_t size;
+
+	mib[3] = code;
+	size = sizeof(value);
+	if (sysctl(mib, sizeof(mib)/sizeof(mib[0]), &value, &size,
+	    &newval, sizeof(newval)) < 0)
+		return -1;
+	else
+		return value;
+}
+
 /*------------------------------------------------------------*/
 
 /* get ia6_flags for link-local addr on if.  returns -1 on error. */
diff --git a/usr.sbin/rtsold/rtsold.8 b/usr.sbin/rtsold/rtsold.8
index 2490890a0766..1e2a3bfa3625 100644
--- a/usr.sbin/rtsold/rtsold.8
+++ b/usr.sbin/rtsold/rtsold.8
@@ -39,15 +39,15 @@
 .\"
 .Sh SYNOPSIS
 .Nm
-.Op Fl dDfm1
+.Op Fl dDfFm1
 .Op Fl O Ar script-name
 .Ar interface ...
 .Nm
-.Op Fl dDfm1
+.Op Fl dDfFm1
 .Op Fl O Ar script-name
 .Fl a
 .Nm rtsol
-.Op Fl dD
+.Op Fl dDF
 .Op Fl O Ar script-name
 .Ar interface ...
 .Nm rtsol
@@ -176,6 +176,18 @@ from becoming a daemon (foreground mode).
 Warning messages are generated to standard error
 instead of
 .Xr syslog 3 .
+.It Fl F
+Configure
+.Xr sysctl 8
+variable related to
+.Nm
+by itself.
+Without
+.Fl F ,
+.Nm
+will not alter and obey the current
+.Xr sysctl 8
+settings.
 .It Fl m
 Enable mobility support.
 If this option is specified,
diff --git a/usr.sbin/rtsold/rtsold.c b/usr.sbin/rtsold/rtsold.c
index e058dd750207..bfdbc68e62e4 100644
--- a/usr.sbin/rtsold/rtsold.c
+++ b/usr.sbin/rtsold/rtsold.c
@@ -62,6 +62,7 @@ struct ifinfo *iflist;
 struct timeval tm_max =	{0x7fffffff, 0x7fffffff};
 static int log_upto = 999;
 static int fflag = 0;
+static int Fflag = 0;	/* force setting sysctl parameters */
 
 int aflag = 0;
 int dflag = 0;
@@ -120,9 +121,9 @@ main(int argc, char **argv)
 	if (argv0 && argv0[strlen(argv0) - 1] != 'd') {
 		fflag = 1;
 		once = 1;
-		opts = "adDO:";
+		opts = "adDFO:";
 	} else
-		opts = "adDfm1O:";
+		opts = "adDfFm1O:";
 
 	while ((ch = getopt(argc, argv, opts)) != -1) {
 		switch (ch) {
@@ -138,6 +139,9 @@ main(int argc, char **argv)
 		case 'f':
 			fflag = 1;
 			break;
+		case 'F':
+			Fflag = 1;
+			break;
 		case 'm':
 			mobile_node = 1;
 			break;
@@ -186,12 +190,17 @@ main(int argc, char **argv)
 	srandom((u_long)time(NULL));
 #endif
 
-	/* warn if accept_rtadv is down */
-	if (!getinet6sysctl(IPV6CTL_ACCEPT_RTADV))
-		warnx("kernel is configured not to accept RAs");
-	/* warn if forwarding is up */
-	if (getinet6sysctl(IPV6CTL_FORWARDING))
-		warnx("kernel is configured as a router, not a host");
+	if (Fflag) {
+		setinet6sysctl(IPV6CTL_ACCEPT_RTADV, 1);
+		setinet6sysctl(IPV6CTL_FORWARDING, 0);
+	} else {
+		/* warn if accept_rtadv is down */
+		if (!getinet6sysctl(IPV6CTL_ACCEPT_RTADV))
+			warnx("kernel is configured not to accept RAs");
+		/* warn if forwarding is up */
+		if (getinet6sysctl(IPV6CTL_FORWARDING))
+			warnx("kernel is configured as a router, not a host");
+	}
 
 	/* initialization to dump internal status to a file */
 	signal(SIGUSR1, rtsold_set_dump_file);
@@ -720,11 +729,11 @@ static void
 usage(char *progname)
 {
 	if (progname && progname[strlen(progname) - 1] != 'd') {
-		fprintf(stderr, "usage: rtsol [-dD] interfaces...\n");
-		fprintf(stderr, "usage: rtsol [-dD] -a\n");
+		fprintf(stderr, "usage: rtsol [-dDF] interfaces...\n");
+		fprintf(stderr, "usage: rtsol [-dDF] -a\n");
 	} else {
-		fprintf(stderr, "usage: rtsold [-adDfm1] interfaces...\n");
-		fprintf(stderr, "usage: rtsold [-dDfm1] -a\n");
+		fprintf(stderr, "usage: rtsold [-adDfFm1] interfaces...\n");
+		fprintf(stderr, "usage: rtsold [-dDfFm1] -a\n");
 	}
 	exit(1);
 }
diff --git a/usr.sbin/rtsold/rtsold.h b/usr.sbin/rtsold/rtsold.h
index 09577a50898f..e25ed955e98f 100644
--- a/usr.sbin/rtsold/rtsold.h
+++ b/usr.sbin/rtsold/rtsold.h
@@ -84,6 +84,7 @@ extern int lladdropt_length __P((struct sockaddr_dl *));
 extern void lladdropt_fill __P((struct sockaddr_dl *, struct nd_opt_hdr *));
 extern struct sockaddr_dl *if_nametosdl __P((char *));
 extern int getinet6sysctl __P((int));
+extern int setinet6sysctl __P((int, int));
 
 /* rtsol.c */
 extern int sockopen __P((void));