diff --git a/ethsock.c b/ethsock.c
index d0c192e..c1674d4 100644
--- a/ethsock.c
+++ b/ethsock.c
@@ -544,18 +544,19 @@ int ethsock_list_all(void)
 	return 0;
 }
 
-int ethsock_is_same_subnet(struct ethsock *sock, struct in_addr *ipaddr,
-		struct in_addr *ipmask)
+int ethsock_for_each_ip(struct ethsock *sock, ethsock_ip_callback_t callback,
+		void *arg)
 {
+	struct ethsock_ip_callback_args args;
 	pcap_if_t *devs, *dev;
 	pcap_addr_t *addr;
-	uint32_t ip, mask, net;
+	int status;
 
 	if (x_pcap_findalldevs(&devs) != 0) {
 		return -1;
 	}
 
-	net = ipaddr->s_addr & ipmask->s_addr;
+	args.arg = arg;
 
 	for (dev = devs; dev; dev = dev->next) {
 		if (strcmp(sock->intf, dev->name)) {
@@ -564,14 +565,20 @@ int ethsock_is_same_subnet(struct ethsock *sock, struct in_addr *ipaddr,
 
 		for (addr = dev->addresses; addr; addr = addr->next) {
 			if (addr->addr->sa_family == AF_INET) {
-				ip = ((struct sockaddr_in*)addr->addr)->sin_addr.s_addr;
-				mask = ((struct sockaddr_in*)addr->netmask)->sin_addr.s_addr;
-				if ((ip & mask) == net) {
-					return 1;
+				args.ipaddr = &((struct sockaddr_in*)addr->addr)->sin_addr;
+				args.ipmask = &((struct sockaddr_in*)addr->netmask)->sin_addr;
+
+				status = callback(&args);
+				if (status <= 0) {
+					break;
 				}
 			}
 		}
+
+		break;
 	}
 
-	return 0;
+	pcap_freealldevs(devs);
+
+	return status <= 0 ? status : 0;
 }
diff --git a/nmrp.c b/nmrp.c
index c9cf6c2..7554929 100644
--- a/nmrp.c
+++ b/nmrp.c
@@ -265,6 +265,40 @@ static int mac_parse(const char *str, uint8_t *hwaddr)
 	return 0;
 }
 
+struct is_valid_ip_arg
+{
+	struct in_addr *ipaddr;
+	struct in_addr *ipmask;
+	int result;
+};
+
+static int is_valid_ip_cb(struct ethsock_ip_callback_args *args)
+{
+#define SUBNET(x) ((x)->ipaddr->s_addr & (x)->ipmask->s_addr)
+	struct is_valid_ip_arg *arg = args->arg;
+	if (SUBNET(args) == SUBNET(arg)) {
+		arg->result = args->ipaddr->s_addr != arg->ipaddr->s_addr;
+		return 0;
+	}
+
+	return 1;
+#undef SUBNET
+}
+
+static int is_valid_ip(struct ethsock *sock, struct in_addr *ipaddr,
+		struct in_addr *ipmask)
+{
+	int status;
+	struct is_valid_ip_arg arg = {
+		.ipaddr = ipaddr,
+		.ipmask = ipmask,
+		.result = 0
+	};
+
+	status = ethsock_for_each_ip(sock, is_valid_ip_cb, &arg);
+	return status < 0 ? status : arg.result;
+}
+
 static struct ethsock *gsock = NULL;
 
 static void sigh(int sig)
@@ -331,13 +365,13 @@ int nmrp_do(struct nmrpd_args *args)
 		return 1;
 	}
 
-	status = ethsock_is_same_subnet(sock, &ipaddr, &ipmask);
+	status = is_valid_ip(sock, &ipaddr, &ipmask);
 	if (status <= 0) {
 		if (!status) {
-			fprintf(stderr, "Address %s/%s invalid for interface %s.\n",
+			fprintf(stderr, "Address %s/%s cannot be used on interface %s.\n",
 					args->ipaddr, args->ipmask, args->intf);
 		}
-		return 1;
+		goto out;
 	}
 
 	gsock = sock;
@@ -494,6 +528,16 @@ int nmrp_do(struct nmrpd_args *args)
 				}
 
 				if (!status && args->file_local) {
+					status = is_valid_ip(sock, &ipaddr, &ipmask);
+					if (status < 0) {
+						goto out;
+					} else if (!status) {
+						printf("IP address of %s has changed. Please assign a "
+								"static ip to the interface.\n", args->intf);
+						tx.msg.code = NMRP_C_CLOSE_REQ;
+						break;
+					}
+
 					if (verbosity) {
 						printf("Using remote filename '%s'.\n",
 								args->file_remote);
diff --git a/nmrpd.h b/nmrpd.h
index f6b7765..0eabf26 100644
--- a/nmrpd.h
+++ b/nmrpd.h
@@ -97,6 +97,15 @@ ssize_t ethsock_recv(struct ethsock *sock, void *buf, size_t len);
 int ethsock_set_timeout(struct ethsock *sock, unsigned msec);
 uint8_t *ethsock_get_hwaddr(struct ethsock *sock);
 int ethsock_list_all(void);
-int ethsock_is_same_subnet(struct ethsock *sock, struct in_addr* ip, struct in_addr *mask);
 
+struct ethsock_ip_callback_args
+{
+	struct in_addr *ipaddr;
+	struct in_addr *ipmask;
+	void *arg;
+};
+
+typedef int (*ethsock_ip_callback_t)(struct ethsock_ip_callback_args *args);
+int ethsock_for_each_ip(struct ethsock *sock, ethsock_ip_callback_t callback,
+		void *arg);
 #endif