Hi,

I have a problem with the SIP message REFER.
I initiate a conference by entering into a conference room, and then I want Freeswitch to add a new participant.
According to the RFC 4579, I sent a REFER message to Freeswitch to add the new participant and I get back a NOTIFY with sipfrag 403 forbidden

I'm working with virtual IP adresses and I'm working only in local

Below is the REFER message I send

REFER sip:3000@192.168.20.3:6060 SIP/2.0
Via: SIP/2.0/UDP 192.168.20.4:7000;branch=z9hG4bKg4534
Max-Forwards: 70
To: <sip:3000@192.168.20.3:6060>;isfocus
From: <sip:1000@192.168.20.4:7000>;tag=1832665346
Call-ID: jbDaf1W7hQtswyvf
CSeq: 1 REFER
Contact: <sip:1000@192.168.20.4:7000>
Allow: INVITE,BYE,REGISTER,ACK,OPTIONS,CANCEL,INFO,PRACK,REFER,MESSAGE,PUBLISH
Allow-Events: REFER
Accept: application/sdp, message/sipfrag
Refer-To: <sip:1001@192.168.20.3:5031;method=INVITE>
Supported: timer, replaces, path
Content-Length: 0


and here is the siptrace of FS

recv 466 bytes from udp/[192.168.20.3]:7000 at 13:21:45.621109:
   ------------------------------------------------------------------------
   REFER sip:3000@192.168.20.3:6060 SIP/2.0
   Via: SIP/2.0/UDP 192.168.20.3:7000;rport;branch=z9hG4bKg4534
   Max-Forwards: 70
   To: <sip:3000@192.168.20.3:6060>;isfocus;tag=g2y4Btme55Fje
   From: <sip:1000@192.168.20.3:7000>;tag=1832665346
   Call-ID: jbDaf1W7hQtswyvf
   CSeq: 476 REFER
   Contact: <sip:1000@192.168.20.3:7000>
   Allow: INVITE,BYE,REGISTER,ACK,OPTIONS,CANCEL,INFO,PRACK,REFER,MESSAGE,PUBLISH
   Refer-To: <sip:1001@192.168.20.3:5001>
   Supported: replaces
   Content-Length: 0
  
   ------------------------------------------------------------------------
2015-08-07 13:21:45.615060 [DEBUG] switch_core_session.c:1061 Send signal sofia/internal/1000@192.168.20.3 [BREAK]
2015-08-07 13:21:45.615060 [DEBUG] switch_core_session.c:978 Send signal sofia/internal/1000@192.168.20.3 [BREAK]
2015-08-07 13:21:45.615060 [DEBUG] sofia.c:7799 Process REFER to [1001@192.168.20.3]
send 722 bytes to udp/[192.168.20.3]:7000 at 13:21:45.624429:
   ------------------------------------------------------------------------
   SIP/2.0 202 Accepted
   Via: SIP/2.0/UDP 192.168.20.3:7000;rport=7000;branch=z9hG4bKg4534
   From: <sip:1000@192.168.20.3:7000>;tag=1832665346
   To: <sip:3000@192.168.20.3:6060>;isfocus;tag=g2y4Btme55Fje
   Call-ID: jbDaf1W7hQtswyvf
   CSeq: 476 REFER
   Contact: <sip:3000@192.168.20.3:6060;transport=udp>
   Expires: 60
   User-Agent: FreeSWITCH-mod_sofia/1.4.20+git~20150701T115426Z~0ae8ee7f8f~64bit
   Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
   Supported: timer, path, replaces
   Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
   Content-Length: 0
  
   ------------------------------------------------------------------------
2015-08-07 13:21:45.615060 [ERR] sofia.c:8297 Cannot Blind Transfer 1 Legged calls
send 888 bytes to udp/[192.168.20.3]:7000 at 13:21:45.624580:
   ------------------------------------------------------------------------
   NOTIFY sip:1000@192.168.20.3:7000 SIP/2.0
   Via: SIP/2.0/UDP 192.168.20.3:6060;rport;branch=z9hG4bKgNeKBK5H869jQ
   Max-Forwards: 70
   From: <sip:3000@192.168.20.3>;isfocus;tag=g2y4Btme55Fje
   To: <sip:1000@192.168.20.3>;tag=1832665346
   Call-ID: jbDaf1W7hQtswyvf
   CSeq: 79137188 NOTIFY
   Contact: <sip:3000@192.168.20.3:6060;transport=udp>
   User-Agent: FreeSWITCH-mod_sofia/1.4.20+git~20150701T115426Z~0ae8ee7f8f~64bit
   Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
   Supported: timer, path, replaces
   Event: refer;id=476
   Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
   Subscription-State: terminated;reason=noresource
   Content-Type: message/sipfrag;version=2.0
   Content-Length: 23
  
   SIP/2.0 403 Forbidden
   ------------------------------------------------------------------------
send 888 bytes to udp/[192.168.20.3]:7000 at 13:21:46.625031:
   ------------------------------------------------------------------------
   NOTIFY sip:1000@192.168.20.3:7000 SIP/2.0
   Via: SIP/2.0/UDP 192.168.20.3:6060;rport;branch=z9hG4bKgNeKBK5H869jQ
   Max-Forwards: 70
   From: <sip:3000@192.168.20.3>;isfocus;tag=g2y4Btme55Fje
   To: <sip:1000@192.168.20.3>;tag=1832665346
   Call-ID: jbDaf1W7hQtswyvf
   CSeq: 79137188 NOTIFY
   Contact: <sip:3000@192.168.20.3:6060;transport=udp>
   User-Agent: FreeSWITCH-mod_sofia/1.4.20+git~20150701T115426Z~0ae8ee7f8f~64bit
   Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
   Supported: timer, path, replaces
   Event: refer;id=476
   Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
   Subscription-State: terminated;reason=noresource
   Content-Type: message/sipfrag;version=2.0
   Content-Length: 23
  
   SIP/2.0 403 Forbidden
   ------------------------------------------------------------------------
send 888 bytes to udp/[192.168.20.3]:7000 at 13:21:48.626014:
   ------------------------------------------------------------------------
   NOTIFY sip:1000@192.168.20.3:7000 SIP/2.0
   Via: SIP/2.0/UDP 192.168.20.3:6060;rport;branch=z9hG4bKgNeKBK5H869jQ
   Max-Forwards: 70
   From: <sip:3000@192.168.20.3>;isfocus;tag=g2y4Btme55Fje
   To: <sip:1000@192.168.20.3>;tag=1832665346
   Call-ID: jbDaf1W7hQtswyvf
   CSeq: 79137188 NOTIFY
   Contact: <sip:3000@192.168.20.3:6060;transport=udp>
   User-Agent: FreeSWITCH-mod_sofia/1.4.20+git~20150701T115426Z~0ae8ee7f8f~64bit
   Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
   Supported: timer, path, replaces
   Event: refer;id=476
   Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
   Subscription-State: terminated;reason=noresource
   Content-Type: message/sipfrag;version=2.0
   Content-Length: 23
  
   SIP/2.0 403 Forbidden


Thanks for your help.