diff -Nur a/system-dummy.c netifd-2019-08-05-5e02f944/system-dummy.c
--- a/system-dummy.c	2020-05-01 17:03:24.807952410 -0700
+++ netifd-2019-08-05-5e02f944/system-dummy.c	2020-05-01 17:03:52.615805779 -0700
@@ -310,6 +310,11 @@
 	return 0;
 }
 
+int system_update_ipv4_mtu(struct device *dev, int mtu)
+{
+	return 0;
+}
+
 int system_update_ipv6_mtu(struct device *dev, int mtu)
 {
 	return 0;
diff -Nur a/system.h netifd-2019-08-05-5e02f944/system.h
--- a/system.h	2020-05-01 17:03:24.807952410 -0700
+++ netifd-2019-08-05-5e02f944/system.h	2020-05-01 17:07:07.894774469 -0700
@@ -253,6 +253,8 @@
 
 void system_fd_set_cloexec(int fd);
 
+int system_update_ipv4_mtu(struct device *device, int mtu);
+
 int system_update_ipv6_mtu(struct device *dev, int mtu);
 
 #endif
diff -Nur a/system-linux.c netifd-2019-08-05-5e02f944/system-linux.c
--- a/system-linux.c	2020-05-01 17:03:24.807952410 -0700
+++ netifd-2019-08-05-5e02f944/system-linux.c	2020-05-01 17:06:12.795065718 -0700
@@ -852,6 +852,12 @@
 	char *oldbr;
 	int ret = 0;
 
+	if (bridge->settings.flags & DEV_OPT_MTU) {
+		system_update_ipv4_mtu(dev, bridge->settings.mtu);
+	}
+	if (bridge->settings.flags & DEV_OPT_MTU6) {
+		system_update_ipv6_mtu(dev, bridge->settings.mtu6);
+	}
 	oldbr = system_get_bridge(dev->ifname, dev_buf, sizeof(dev_buf));
 	if (!oldbr || strcmp(oldbr, bridge->ifname) != 0)
 		ret = system_bridge_if(bridge->ifname, dev, SIOCBRADDIF, NULL);
@@ -1526,10 +1532,9 @@
 	memset(&ifr, 0, sizeof(ifr));
 	strncpy(ifr.ifr_name, dev->ifname, sizeof(ifr.ifr_name) - 1);
 
-	if (ioctl(sock_ioctl, SIOCGIFMTU, &ifr) == 0) {
-		s->mtu = ifr.ifr_mtu;
+	s->mtu = system_update_ipv4_mtu(dev, 0);
+	if (s->mtu > 0)
 		s->flags |= DEV_OPT_MTU;
-	}
 
 	s->mtu6 = system_update_ipv6_mtu(dev, 0);
 	if (s->mtu6 > 0)
@@ -1623,8 +1628,7 @@
 	memset(&ifr, 0, sizeof(ifr));
 	strncpy(ifr.ifr_name, dev->ifname, sizeof(ifr.ifr_name) - 1);
 	if (s->flags & DEV_OPT_MTU & apply_mask) {
-		ifr.ifr_mtu = s->mtu;
-		if (ioctl(sock_ioctl, SIOCSIFMTU, &ifr) < 0)
+		if (system_update_ipv4_mtu(dev, s->mtu) < 0)
 			s->flags &= ~DEV_OPT_MTU;
 	}
 	if (s->flags & DEV_OPT_MTU6 & apply_mask) {
@@ -3360,12 +3364,42 @@
 	return __system_del_ip_tunnel(name, tb);
 }
 
+int system_update_ipv4_mtu(struct device *dev, int mtu)
+{
+	int ret = -1;
+	struct ifreq ifr;
+
+	if(!dev)
+		return ret;
+
+	memset(&ifr, 0, sizeof(ifr));
+	ifr.ifr_addr.sa_family = AF_INET;
+	strncpy(ifr.ifr_name, dev->ifname, sizeof(ifr.ifr_name));
+
+	if (!mtu) {
+		ret = ioctl(sock_ioctl, SIOCGIFMTU, &ifr);
+		if (ret == 0)
+			ret = ifr.ifr_mtu;
+	} else {
+		struct device * parent = system_if_get_parent(dev);
+		if (parent)
+			system_update_ipv4_mtu(parent, mtu);
+
+		ifr.ifr_mtu = mtu;
+		ret = ioctl(sock_ioctl, SIOCSIFMTU, &ifr);
+	}
+	return (ret == 0)?mtu:ret;
+}
+
 int system_update_ipv6_mtu(struct device *dev, int mtu)
 {
 	int ret = -1;
 	char buf[64];
 	int fd;
 
+	if(!dev)
+		return ret;
+
 	snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/conf/%s/mtu",
 			dev->ifname);