diff --git a/ptp4l.c b/ptp4l.c
index c75e8ce..c50384b 100644
--- a/ptp4l.c
+++ b/ptp4l.c
@@ -22,6 +22,7 @@
 #include <unistd.h>
 
 #include "clock.h"
+#include "config.h"
 #include "print.h"
 #include "transport.h"
 #include "udp.h"
@@ -30,6 +31,7 @@
 
 static int running = 1;
 static struct defaultDS ds;
+static struct port_defaults pod;
 
 static int generate_clock_identity(struct ClockIdentity *ci, char *name)
 {
@@ -60,11 +62,12 @@ static void usage(char *progname)
 		" -s        SOFTWARE\n"
 		" -z        LEGACY HW\n\n"
 		" Other Options\n\n"
+		" -f [file] read configuration from 'file'\n"
 		" -h        prints this message and exits\n"
 		" -i [dev]  interface device to use, for example 'eth0'\n"
 		"           (may be specified multiple times)\n"
 		" -l [num]  set the logging level to 'num'\n"
-		" -m        slave only mode\n"
+		" -m        slave only mode (overrides configuration file)\n"
 		" -p [dev]  PTP hardware clock device to use, default '%s'\n"
 		"           (ignored for SOFTWARE/LEGACY HW time stamping)\n\n",
 		progname, DEFAULT_PHC);
@@ -72,7 +75,7 @@ static void usage(char *progname)
 
 int main(int argc, char *argv[])
 {
-	char *phc = DEFAULT_PHC, *progname;
+	char *config = NULL, *phc = DEFAULT_PHC, *progname;
 	int c, i, nports = 0, slaveonly = 0;
 	struct interface iface[MAX_PORTS];
 	enum transport_type transport = TRANS_UDP_IPV4;
@@ -82,7 +85,7 @@ int main(int argc, char *argv[])
 	/* Process the command line arguments. */
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "246hi:l:mp:rsz"))) {
+	while (EOF != (c = getopt(argc, argv, "246f:hi:l:mp:rsz"))) {
 		switch (c) {
 		case '2':
 			transport = TRANS_IEEE_802_3;
@@ -93,6 +96,9 @@ int main(int argc, char *argv[])
 		case '6':
 			transport = TRANS_UDP_IPV6;
 			break;
+		case 'f':
+			config = optarg;
+			break;
 		case 'i':
 			if (nports < MAX_PORTS) {
 				iface[nports++].name = optarg;
@@ -143,9 +149,9 @@ int main(int argc, char *argv[])
 		phc = NULL;
 	}
 
-	ds.slaveOnly = slaveonly ? TRUE : FALSE;
+	ds.slaveOnly = FALSE;
 	ds.priority1 = 128;
-	ds.clockQuality.clockClass = slaveonly ? 255 : 248;
+	ds.clockQuality.clockClass = 248;
 	ds.clockQuality.clockAccuracy = 0xfe;
 	ds.clockQuality.offsetScaledLogVariance = 0xffff;
 	ds.priority2 = 128;
@@ -155,6 +161,16 @@ int main(int argc, char *argv[])
 		return -1;
 	}
 
+	if (config && config_read(config, &ds, &pod)) {
+		fprintf(stderr, "failed to read configuration file\n");
+		return -1;
+	}
+
+	if (slaveonly) {
+		ds.slaveOnly = TRUE;
+		ds.clockQuality.clockClass = 255;
+	}
+
 	clock = clock_create(phc, iface, nports, &ds);
 	if (!clock) {
 		fprintf(stderr, "failed to create a clock\n");