Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 45305)
+++ channels/chan_sip.c	(working copy)
@@ -468,6 +468,7 @@
 #define DEFAULT_ALLOWGUEST	TRUE
 #define DEFAULT_SRVLOOKUP	FALSE		/*!< Recommended setting is ON */
 #define DEFAULT_COMPACTHEADERS	FALSE
+#define DEFAULT_RTPIP   "auto"
 #define DEFAULT_TOS_SIP         0               /*!< Call signalling packets should be marked as DSCP CS3, but the default is 0 to be compatible with previous versions. */
 #define DEFAULT_TOS_AUDIO       0               /*!< Audio packets should be marked as DSCP EF (Expedited Forwarding), but the default is 0 to be compatible with previous versions. */
 #define DEFAULT_TOS_VIDEO       0               /*!< Video packets should be marked as DSCP AF41, but the default is 0 to be compatible with previous versions. */
@@ -526,6 +527,7 @@
 static char global_realm[MAXHOSTNAMELEN]; 		/*!< Default realm */
 static char global_regcontext[AST_MAX_CONTEXT];		/*!< Context for auto-extensions */
 static char global_useragent[AST_MAX_EXTENSION];	/*!< Useragent for the SIP channel */
+static char global_rtpip[AST_MAX_EXTENSION];    /*!< Specify IP endpoint for RTP SDP message */
 static int allow_external_domains;	/*!< Accept calls to external SIP domains? */
 static int global_callevents;		/*!< Whether we send manager events or not */
 static int global_t1min;		/*!< T1 roundtrip time minimum */
@@ -5771,11 +5773,21 @@
 			p->t38.peercapability,
 			p->t38.jointcapability);
 	}
-	snprintf(v, sizeof(v), "v=0\r\n");
-	snprintf(o, sizeof(o), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, ast_inet_ntoa(udptldest.sin_addr));
-	snprintf(s, sizeof(s), "s=session\r\n");
-	snprintf(c, sizeof(c), "c=IN IP4 %s\r\n", ast_inet_ntoa(udptldest.sin_addr));
-	snprintf(t, sizeof(t), "t=0 0\r\n");
+	
+	/* Replace RTP IP address, if rtpip!=auto */
+	if (!strcasestr(global_rtpip, "auto")) {
+	    snprintf(v, sizeof(v), "v=0\r\n");
+ 	    snprintf(o, sizeof(o), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, global_rtpip);
+	    snprintf(s, sizeof(s), "s=session\r\n");
+	    snprintf(c, sizeof(c), "c=IN IP4 %s\r\n", global_rtpip);
+	    snprintf(t, sizeof(t), "t=0 0\r\n");
+	} else {
+         snprintf(v, sizeof(v), "v=0\r\n");
+ 	    snprintf(o, sizeof(o), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, ast_inet_ntoa(udptldest.sin_addr));
+	    snprintf(s, sizeof(s), "s=session\r\n");
+	    snprintf(c, sizeof(c), "c=IN IP4 %s\r\n", ast_inet_ntoa(udptldest.sin_addr));
+	    snprintf(t, sizeof(t), "t=0 0\r\n");
+	}
 	ast_build_string(&m_modem_next, &m_modem_left, "m=image %d udptl t38\r\n", ntohs(udptldest.sin_port));
 	
 	if ((p->t38.jointcapability & T38FAX_VERSION) == T38FAX_VERSION_0)
@@ -5979,8 +5991,15 @@
 	/* We break with the "recommendation" and send our IP, in order that our
 	   peer doesn't have to ast_gethostbyname() us */
 
-	snprintf(owner, sizeof(owner), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, ast_inet_ntoa(dest.sin_addr));
-	snprintf(connection, sizeof(connection), "c=IN IP4 %s\r\n", ast_inet_ntoa(dest.sin_addr));
+	/* Replace RTP IP address, if rtpip!=auto */
+	if (!strcasestr(global_rtpip, "auto")) {
+	    snprintf(owner, sizeof(owner), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, global_rtpip);
+	    snprintf(connection, sizeof(connection), "c=IN IP4 %s\r\n", global_rtpip);
+	} else {
+         snprintf(owner, sizeof(owner), "o=root %d %d IN IP4 %s\r\n", p->sessionid, p->sessionversion, ast_inet_ntoa(dest.sin_addr));
+	    snprintf(connection, sizeof(connection), "c=IN IP4 %s\r\n", ast_inet_ntoa(dest.sin_addr));
+	}
+
 	ast_build_string(&m_audio_next, &m_audio_left, "m=audio %d RTP/AVP", ntohs(dest.sin_port));
 
 	if (ast_test_flag(&p->flags[1], SIP_PAGE2_CALL_ONHOLD_ONEDIR))
@@ -15637,6 +15656,7 @@
 	global_notifyringing = DEFAULT_NOTIFYRINGING;
 	global_alwaysauthreject = 0;
 	global_allowsubscribe = FALSE;
+	ast_copy_string(global_rtpip, DEFAULT_RTPIP, sizeof(global_rtpip));
 	ast_copy_string(global_useragent, DEFAULT_USERAGENT, sizeof(global_useragent));
 	ast_copy_string(default_notifymime, DEFAULT_NOTIFYMIME, sizeof(default_notifymime));
 	if (ast_strlen_zero(ast_config_AST_SYSTEM_NAME))
@@ -15752,6 +15772,8 @@
 				ast_log(LOG_WARNING, "'%s' is not a valid RTP keepalive time at line %d.  Using default.\n", v->value, v->lineno);
 				global_rtpkeepalive = 0;
 			}
+		} else if (!strcasecmp(v->name, "rtpip")) {
+            ast_copy_string(global_rtpip, v->value, sizeof(global_rtpip));
 		} else if (!strcasecmp(v->name, "compactheaders")) {
 			compactheaders = ast_true(v->value);
 		} else if (!strcasecmp(v->name, "notifymimetype")) {