diff -urN asterisk-1.4.23.1_orig/channels/chan_sip.c asterisk-1.4.23.1/channels/chan_sip.c
--- asterisk-1.4.23.1_orig/channels/chan_sip.c	2009-01-31 00:20:49.000000000 +0100
+++ asterisk-1.4.23.1/channels/chan_sip.c	2009-01-31 00:22:17.000000000 +0100
@@ -9397,6 +9397,7 @@
 {
 	char via[512];
 	char *c, *pt;
+	char *maddr;
 	struct hostent *hp;
 	struct ast_hostent ahp;
 
@@ -9412,8 +9413,16 @@
 	if (c && (c[6] != '='))	/* rport query, not answer */
 		ast_set_flag(&p->flags[0], SIP_NAT_ROUTE);
 
+	/* Check for maddr */
+	maddr = strstr(via, "maddr=");
+	if (maddr) {
+		maddr += 6;
+		c = maddr + strspn(maddr, "0123456789.");
+		*c = '\0';
+	}
+
 	c = strchr(via, ';');
-	if (c) 
+	if (c)
 		*c = '\0';
 
 	c = strchr(via, ' ');
@@ -9427,6 +9436,9 @@
 		pt = strchr(c, ':');
 		if (pt)
 			*pt++ = '\0';	/* remember port pointer */
+		/* use maddr if found */
+		if (maddr)
+			c = maddr;
 		hp = ast_gethostbyname(c, &ahp);
 		if (!hp) {
 			ast_log(LOG_WARNING, "'%s' is not a valid host\n", c);