Index: sys/net/debugnet_inet.c
===================================================================
--- sys/net/debugnet_inet.c
+++ sys/net/debugnet_inet.c
@@ -347,13 +347,19 @@
 			    " server or gateway)\n", buf);
 			return;
 		}
+		if (pcb->dp_state >= DN_STATE_HAVE_GW_MAC) {
+			inet_ntoa_r(isaddr, buf);
+			DNETDEBUG("ignoring server ARP reply from %s (already"
+			    " have gateway address)\n", buf);
+			return;
+		}
+		MPASS(pcb->dp_state == DN_STATE_INIT);
 		memcpy(pcb->dp_gw_mac.octet, ar_sha(ah),
 		    min(ah->ar_hln, ETHER_ADDR_LEN));
 		
 		DNETDEBUG("got server MAC address %6D\n",
 		    pcb->dp_gw_mac.octet, ":");
 
-		MPASS(pcb->dp_state == DN_STATE_INIT);
 		pcb->dp_state = DN_STATE_HAVE_GW_MAC;
 		return;
 	}