Index: config.c
===================================================================
--- config.c	(revision 43)
+++ config.c	(working copy)
@@ -283,6 +283,13 @@
 		if (addr == NULL)
 			continue;
 
+		if (agetflag("noprefix")) {
+			syslog(LOG_ERR,
+			    "noprefix is set but addr is set (%s); ignoring",
+			    addr);
+			continue;
+		}
+
 		/* allocate memory to store prefix information */
 		if ((pfx = malloc(sizeof(struct prefix))) == NULL) {
 			syslog(LOG_ERR,
@@ -381,7 +388,7 @@
 				now.tv_sec + pfx->preflifetime;
 		}
 	}
-	if (tmp->pfxs == 0)
+	if (tmp->pfxs == 0 && !agetflag("noprefix"))
 		get_prefix(tmp);
 
 	MAYHAVE(val, "mtu", 0);