I have a trouble, when FS start it register whit Siemens pbx, but after FS loses registration.  I have a x-lite registered whit Siemens pbx and x-lite keeps register.
 
I add whireshark trace 

thank you
 
Diego
------------------------------------------------------
  1. whireshark trace  (register nok)
  2.  
  3.  
  4.  
  5. VIA (x-lite):
  6. Via: SIP/2.0/UDP 192.168.0.125:27504;branch=z9hG4bK-d8754z-ed554d5f6c56a345-1---d8754z-;rport
  7. Transport: UDP
  8. Sent-by Address: 192.168.0.125
  9. Sent-by port: 27504
  10. Branch: z9hG4bK-d8754z-ed554d5f6c56a345-1---d8754z-
  11. RPort: rport
  12. Max-Forwards: 70
  13.  
  14.  
  15. VIA (FS)
  16. Via: SIP/2.0/UDP 192.168.0.125:5080;rport;branch=z9hG4bKc2BX53H64t2ta
  17. Transport: UDP
  18. Sent-by Address: 192.168.0.125
  19. Sent-by port: 5080
  20. RPort: rport
  21. Branch: z9hG4bKc2BX53H64t2ta
  22. Max-Forwards: 70
  23.  
  24.  
  25. To (x-lite)
  26. To: "135"<sip:135@192.168.0.120>
  27. SIP Display info: "135"
  28. SIP to address: sip:135@192.168.0.120
  29.  
  30. To (FS)
  31. To: <sip:134@192.168.0.120;transport=udp>
  32. SIP to address: sip:134@192.168.0.120
  33.  
  34.  
  35. contact (x-lite)
  36. Contact: <sip:135@192.168.0.125:27504;rinstance=21711995165dd606>
  37.  Contact Binding: <sip:135@192.168.0.125:27504;rinstance=21711995165dd606>
  38.    URI: <sip:135@192.168.0.125:27504;rinstance=21711995165dd606>
  39.      SIP contact address: sip:135@192.168.0.125:27504
  40.  
  41. contact (FS)
  42. Contact: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  43.  Contact Binding: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  44.   URI: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  45.     SIP contact address: sip:gw+siemens3500@192.168.0.125:5080
  46. Expires: 0
  47.  
  48.  
  49.  
  50. =============================
  51.  
  52. FS start up whireshark trace  (register ok)
  53.  
  54.  
  55. To: <sip:134@192.168.0.120;transport=udp>
  56. SIP to address: sip:134@192.168.0.120
  57. Call-ID: 27c589ef-6e9a-5544-887a-52c0c7856977
  58.  
  59.  
  60. Contact: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  61.  Contact Binding: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  62.   URI: <sip:gw+siemens3500@192.168.0.125:5080;tport=tcp;transport=udp>
  63.     SIP contact address: sip:gw+siemens3500@192.168.0.125:5080
  64. Expires: 120
  65.  
  66.  
  67. Via: SIP/2.0/UDP 192.168.0.125:5080;rport;branch=z9hG4bKBB461XN46BmcK
  68. Transport: UDP
  69. Sent-by Address: 192.168.0.125
  70. Sent-by port: 5080
  71. RPort: rport
  72. Branch: z9hG4bKBB461XN46BmcK
  73. Max-Forwards: 70