diff --git a/ethsock.c b/ethsock.c
index 1c6a039..f8fdf23 100644
--- a/ethsock.c
+++ b/ethsock.c
@@ -38,6 +38,12 @@ struct ethsock
 	uint8_t hwaddr[6];
 };
 
+struct ethsock_arp_undo
+{
+	uint32_t ipaddr;
+	uint8_t hwaddr[6];
+};
+
 struct ethsock_ip_undo
 {
 #ifndef NMRPFLASH_WINDOWS
@@ -455,50 +461,66 @@ inline int ethsock_set_timeout(struct ethsock *sock, unsigned msec)
 }
 
 #ifndef NMRPFLASH_WINDOWS
-int ethsock_arp_add(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr)
+int ethsock_arp_add(struct ethsock *sock, uint8_t *hwaddr, uint32_t ipaddr, struct ethsock_arp_undo **undo)
 {
 	return 0;
 }
 
-int ethsock_arp_del(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr)
+int ethsock_arp_del(struct ethsock *sock, struct ethsock_arp_undo **undo)
 {
 	return 0;
 }
 #else
-static int ethsock_arp(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr, int add)
+static int ethsock_arp(struct ethsock *sock, uint8_t *hwaddr, uint32_t ipaddr, struct ethsock_arp_undo **undo)
 {
 	DWORD ret;
 	MIB_IPNETROW arp = {
 		.dwIndex = sock->index,
 		.dwPhysAddrLen = 6,
-		.dwAddr = ipaddr->s_addr,
+		.dwAddr = ipaddr,
 		.dwType = MIB_IPNET_TYPE_STATIC
 	};
-	
+
 	memcpy(arp.bPhysAddr, hwaddr, 6);
-	
-	if (add) {
+
+	if (undo) {
 		ret = CreateIpNetEntry(&arp);
 		if (ret != NO_ERROR) {
 			win_perror2("CreateIpNetEntry", ret);
 			return -1;
 		}
+
+		*undo = malloc(sizeof(struct ethsock_arp_undo));
+		if (!*undo) {
+			perror("malloc");
+			return -1;
+		}
+
+		(*undo)->ipaddr = ipaddr;
+		memcpy((*undo)->hwaddr, hwaddr, 6);
 	} else {
 		DeleteIpNetEntry(&arp);
 	}
-	
+
 	return 0;
 }
 
-int ethsock_arp_add(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr)
+int ethsock_arp_add(struct ethsock *sock, uint8_t *hwaddr, uint32_t ipaddr, struct ethsock_arp_undo **undo)
 {
-	ethsock_arp_del(sock, hwaddr, ipaddr);
-	return ethsock_arp(sock, hwaddr, ipaddr, 1);
+	ethsock_arp(sock, hwaddr, ipaddr, NULL);
+	return undo ? ethsock_arp(sock, hwaddr, ipaddr, undo) : -1;
 }
 
-int ethsock_arp_del(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr)
+int ethsock_arp_del(struct ethsock *sock, struct ethsock_arp_undo **undo)
 {
-	return ethsock_arp(sock, hwaddr, ipaddr, 0);
+	if (!*undo) {
+		return 0;
+	}
+
+	int ret = ethsock_arp(sock, (*undo)->hwaddr, (*undo)->ipaddr, NULL);
+	free(*undo);
+	*undo = NULL;
+	return ret;
 }
 #endif
 
diff --git a/nmrp.c b/nmrp.c
index 0d39259..da665cf 100644
--- a/nmrp.c
+++ b/nmrp.c
@@ -386,19 +386,15 @@ static int is_valid_ip(struct ethsock *sock, struct in_addr *ipaddr,
 }
 
 static struct ethsock *gsock = NULL;
-static struct ethsock_ip_undo *gundo = NULL;
-static int garp = 0;
-static struct in_addr arpip = { 0 };
-static uint8_t arpmac[6] = { 0 };
+static struct ethsock_ip_undo *g_ip_undo = NULL;
+static struct ethsock_arp_undo *g_arp_undo = NULL;
 
 static void sigh(int sig)
 {
 	printf("\n");
 	if (gsock) {
-		if (garp) {
-			ethsock_arp_del(gsock, arpmac, &arpip);
-		}
-		ethsock_ip_del(gsock, &gundo);
+		ethsock_arp_del(gsock, &g_arp_undo);
+		ethsock_ip_del(gsock, &g_ip_undo);
 		ethsock_close(gsock);
 		gsock = NULL;
 	}
@@ -496,7 +492,6 @@ int nmrp_do(struct nmrpd_args *args)
 	}
 
 	gsock = sock;
-	garp = 0;
 	sigh_orig = signal(SIGINT, sigh);
 
 	if (!autoip) {
@@ -513,7 +508,7 @@ int nmrp_do(struct nmrpd_args *args)
 			printf("Adding %s to interface %s.\n", args->ipaddr_intf, args->intf);
 		}
 
-		if (ethsock_ip_add(sock, intf_addr, ipconf.mask.s_addr, &gundo) != 0) {
+		if (ethsock_ip_add(sock, intf_addr, ipconf.mask.s_addr, &g_ip_undo) != 0) {
 			goto out;
 		}
 	}
@@ -609,15 +604,10 @@ int nmrp_do(struct nmrpd_args *args)
 				printf("Sending configuration: %s, netmask %s.\n",
 						args->ipaddr, args->ipmask);
 
-				memcpy(arpmac, rx.eh.ether_shost, 6);
-				memcpy(&arpip, &ipconf.addr, sizeof(ipconf.addr));
-
-				if (ethsock_arp_add(sock, arpmac, &arpip) != 0) {
+				if (ethsock_arp_add(sock, rx.eh.ether_shost, ipconf.addr.s_addr, &g_arp_undo) != 0) {
 					goto out;
 				}
 
-				garp = 1;
-
 				break;
 			case NMRP_C_TFTP_UL_REQ:
 				if (!upload_ok) {
@@ -760,8 +750,8 @@ int nmrp_do(struct nmrpd_args *args)
 out:
 	signal(SIGINT, sigh_orig);
 	gsock = NULL;
-	ethsock_arp_del(sock, arpmac, &arpip);
-	ethsock_ip_del(sock, &gundo);
+	ethsock_arp_del(sock, &g_arp_undo);
+	ethsock_ip_del(sock, &g_ip_undo);
 	ethsock_close(sock);
 	return status;
 }
diff --git a/nmrpd.h b/nmrpd.h
index 2e85012..e061155 100644
--- a/nmrpd.h
+++ b/nmrpd.h
@@ -104,6 +104,7 @@ void sock_perror(const char *msg);
 extern int verbosity;
 
 struct ethsock;
+struct ethsock_arp_undo;
 struct ethsock_ip_undo;
 
 struct ethsock *ethsock_create(const char *intf, uint16_t protocol);
@@ -112,8 +113,8 @@ int ethsock_send(struct ethsock *sock, void *buf, size_t len);
 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_arp_add(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr);
-int ethsock_arp_del(struct ethsock *sock, uint8_t *hwaddr, struct in_addr *ipaddr);
+int ethsock_arp_add(struct ethsock *sock, uint8_t *hwaddr, uint32_t ipaddr, struct ethsock_arp_undo **undo);
+int ethsock_arp_del(struct ethsock *sock, struct ethsock_arp_undo **undo);
 int ethsock_list_all(void);
 
 struct ethsock_ip_callback_args