diff -Naur twinkle-1.1-orig/src/phone.cpp twinkle/twinkle-1.0.1/src/phone.cpp
--- twinkle-1.1-orig/src/phone.cpp	2007-11-02 21:00:00.000000000 +0100
+++ twinkle-1.1-nat/src/phone.cpp	2007-11-02 21:01:24.000000000 +0100
@@ -2793,6 +2793,16 @@
 	return result;
 }
 
+string t_phone::get_call_id_ip_sip(t_user *user) {
+	string result;
+
+	lock();
+	result = LOCAL_IP;
+	unlock();
+	
+	return result;
+}
+
 unsigned short t_phone::get_public_port_sip(const t_user *user) const {
 	unsigned short result;
 	
diff -Naur twinkle-1.1-orig/src/phone.h twinkle/twinkle-1.0.1/src/phone.h
--- twinkle-1.1-orig/src/phone.h	2007-11-02 21:00:00.000000000 +0100
+++ twinkle-1.1-nat/src/phone.h	2007-11-02 21:01:44.000000000 +0100
@@ -422,6 +422,7 @@
 	
 	// Get IP address and port for SIP
 	string get_ip_sip(const t_user *user) const;
+	string get_call_id_ip_sip(t_user *user);
 	unsigned short get_public_port_sip(const t_user *user) const;
 	
 	// Indicates if STUN is used
diff -Naur twinkle-1.1-orig/src/protocol.h twinkle/twinkle-1.0.1/src/protocol.h
--- twinkle-1.1-orig/src/protocol.h	2007-11-02 21:00:00.000000000 +0100
+++ twinkle-1.1-nat/src/protocol.h	2007-11-02 21:03:06.000000000 +0100
@@ -214,7 +214,7 @@
 #define CALL_ID_LEN	15
 
 // Create a new call-id
-#define NEW_CALL_ID(u)	(random_token(CALL_ID_LEN) + '@' + USER_HOST(u))
+#define NEW_CALL_ID(u)	(random_token(CALL_ID_LEN) + '@' + CALL_ID_USER_HOST(u))
 
 // Create a new sequence number fo CSeq header
 #define NEW_SEQNR	rand() % 1000 + 1
diff -Naur twinkle-1.1-orig/src/user.h twinkle/twinkle-1.0.1/src/user.h
--- twinkle-1.1-orig/src/user.h	2007-11-02 21:00:00.000000000 +0100
+++ twinkle-1.1-nat/src/user.h	2007-11-02 21:03:52.000000000 +0100
@@ -43,6 +43,7 @@
 
 #define PUBLIC_SIP_UDP_PORT(u)	phone->get_public_port_sip(u)
 #define USER_HOST(u)		phone->get_ip_sip(u)
+#define CALL_ID_USER_HOST(u)		phone->get_call_id_ip_sip(u)
 #define LOCAL_IP		user_host
 
 #define SPECIAL_PHONE_SYMBOLS	"-()/."