oups... je suis aller un peu vite:

Code:
# sudo ngrep -d eth0 port 5060 and host ippi.fr
interface: eth0 (192.168.1.0/255.255.255.0)
filter: (ip or ip6) and ( port 5060 and host ippi.fr )
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  OPTIONS sip:ippi.fr SIP/2.0..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK4b893a70;rport..Max-Forwards: 70..From: "asterisk" <sip:asterisk@84.10
  0.202.211>;tag=as36afd3b9..To: <sip:ippi.fr>..Contact: <sip:asterisk@84.100
  .202.211>..Call-ID: 7506157c6774cb4d28df222b6a5fe13d@84.100.202.211..CSeq: 
  102 OPTIONS..User-Agent: Asterisk PBX 1.6.2.5-0ubuntu1.3..Date: Tue, 28 Jun
   2011 20:58:45 GMT..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCR
  IBE, NOTIFY, INFO..Supported: replaces, timer..Content-Length: 0....       
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  SIP/2.0 404 unknown service..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK4b893a70;rport=5060..From: "asterisk" <sip:asterisk@84.100.202.211>;ta
  g=as36afd3b9..To: <sip:ippi.fr>;tag=a910c8153188470b2841623c513a131f.da22..
  Call-ID: 7506157c6774cb4d28df222b6a5fe13d@84.100.202.211..CSeq: 102 OPTIONS
  ..Server: OpenSIPS (1.6.3-notls (i386/linux))..Content-Length: 0....       
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  OPTIONS sip:84.100.202.211:5060 SIP/2.0..Via: SIP/2.0/UDP 213.215.45.230:50
  60;branch=0..From: sip:pinger@ippi.fr;tag=8cf0798a..To: sip:84.100.202.211:
  5060..Call-ID: 0be50fc6-ecc13844-30e16b@213.215.45.230..CSeq: 1 OPTIONS..Co
  ntent-Length: 0....                                                        
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  SIP/2.0 200 OK..Via: SIP/2.0/UDP 213.215.45.230:5060;branch=0;received=213.
  215.45.230..From: sip:pinger@ippi.fr;tag=8cf0798a..To: sip:84.100.202.211:5
  060;tag=as325c3a56..Call-ID: 0be50fc6-ecc13844-30e16b@213.215.45.230..CSeq:
   1 OPTIONS..Server: Asterisk PBX 1.6.2.5-0ubuntu1.3..Allow: INVITE, ACK, CA
  NCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replaces, ti
  mer..Contact: <sip:84.100.202.211>..Accept: application/sdp..Content-Length
  : 0....                                                                    
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  OPTIONS sip:84.100.202.211:5060 SIP/2.0..Via: SIP/2.0/UDP 213.215.45.230:50
  60;branch=0..From: sip:pinger@ippi.fr;tag=1c71798a..To: sip:84.100.202.211:
  5060..Call-ID: 0be50fc6-7c423844-12e16b@213.215.45.230..CSeq: 1 OPTIONS..Co
  ntent-Length: 0....                                                        
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  SIP/2.0 200 OK..Via: SIP/2.0/UDP 213.215.45.230:5060;branch=0;received=213.
  215.45.230..From: sip:pinger@ippi.fr;tag=1c71798a..To: sip:84.100.202.211:5
  060;tag=as5566a8e1..Call-ID: 0be50fc6-7c423844-12e16b@213.215.45.230..CSeq:
   1 OPTIONS..Server: Asterisk PBX 1.6.2.5-0ubuntu1.3..Allow: INVITE, ACK, CA
  NCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replaces, ti
  mer..Contact: <sip:84.100.202.211>..Accept: application/sdp..Content-Length
  : 0....                                                                    
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  OPTIONS sip:ippi.fr SIP/2.0..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK3800ff10;rport..Max-Forwards: 70..From: "asterisk" <sip:asterisk@84.10
  0.202.211>;tag=as04fc9999..To: <sip:ippi.fr>..Contact: <sip:asterisk@84.100
  .202.211>..Call-ID: 38042a5364d1367c455afba91cb83e2e@84.100.202.211..CSeq: 
  102 OPTIONS..User-Agent: Asterisk PBX 1.6.2.5-0ubuntu1.3..Date: Tue, 28 Jun
   2011 20:59:45 GMT..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCR
  IBE, NOTIFY, INFO..Supported: replaces, timer..Content-Length: 0....       
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  SIP/2.0 404 unknown service..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK3800ff10;rport=5060..From: "asterisk" <sip:asterisk@84.100.202.211>;ta
  g=as04fc9999..To: <sip:ippi.fr>;tag=a910c8153188470b2841623c513a131f.3963..
  Call-ID: 38042a5364d1367c455afba91cb83e2e@84.100.202.211..CSeq: 102 OPTIONS
  ..Server: OpenSIPS (1.6.3-notls (i386/linux))..Content-Length: 0....       
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  OPTIONS sip:84.100.202.211:5060 SIP/2.0..Via: SIP/2.0/UDP 213.215.45.230:50
  60;branch=0..From: sip:pinger@ippi.fr;tag=bbf1798a..To: sip:84.100.202.211:
  5060..Call-ID: 0be50fc6-1cc23844-f3e16b@213.215.45.230..CSeq: 1 OPTIONS..Co
  ntent-Length: 0....                                                        
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  SIP/2.0 200 OK..Via: SIP/2.0/UDP 213.215.45.230:5060;branch=0;received=213.
  215.45.230..From: sip:pinger@ippi.fr;tag=bbf1798a..To: sip:84.100.202.211:5
  060;tag=as55ec95a4..Call-ID: 0be50fc6-1cc23844-f3e16b@213.215.45.230..CSeq:
   1 OPTIONS..Server: Asterisk PBX 1.6.2.5-0ubuntu1.3..Allow: INVITE, ACK, CA
  NCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replaces, ti
  mer..Contact: <sip:84.100.202.211>..Accept: application/sdp..Content-Length
  : 0....                                                                    
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  OPTIONS sip:84.100.202.211:5060 SIP/2.0..Via: SIP/2.0/UDP 213.215.45.230:50
  60;branch=0..From: sip:pinger@ippi.fr;tag=8b72798a..To: sip:84.100.202.211:
  5060..Call-ID: 0be50fc6-eb433844-d5e16b@213.215.45.230..CSeq: 1 OPTIONS..Co
  ntent-Length: 0....                                                        
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  SIP/2.0 200 OK..Via: SIP/2.0/UDP 213.215.45.230:5060;branch=0;received=213.
  215.45.230..From: sip:pinger@ippi.fr;tag=8b72798a..To: sip:84.100.202.211:5
  060;tag=as301bad47..Call-ID: 0be50fc6-eb433844-d5e16b@213.215.45.230..CSeq:
   1 OPTIONS..Server: Asterisk PBX 1.6.2.5-0ubuntu1.3..Allow: INVITE, ACK, CA
  NCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replaces, ti
  mer..Contact: <sip:84.100.202.211>..Accept: application/sdp..Content-Length
  : 0....                                                                    
#
U 192.168.1.100:5060 -> 213.215.45.230:5060
  OPTIONS sip:ippi.fr SIP/2.0..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK29ab842a;rport..Max-Forwards: 70..From: "asterisk" <sip:asterisk@84.10
  0.202.211>;tag=as78edc5e1..To: <sip:ippi.fr>..Contact: <sip:asterisk@84.100
  .202.211>..Call-ID: 3f39c9310f5f93c56dced2c632df3344@84.100.202.211..CSeq: 
  102 OPTIONS..User-Agent: Asterisk PBX 1.6.2.5-0ubuntu1.3..Date: Tue, 28 Jun
   2011 21:00:45 GMT..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCR
  IBE, NOTIFY, INFO..Supported: replaces, timer..Content-Length: 0....       
#
U 213.215.45.230:5060 -> 192.168.1.100:5060
  SIP/2.0 404 unknown service..Via: SIP/2.0/UDP 84.100.202.211:5060;branch=z9
  hG4bK29ab842a;rport=5060..From: "asterisk" <sip:asterisk@84.100.202.211>;ta
  g=as78edc5e1..To: <sip:ippi.fr>;tag=a910c8153188470b2841623c513a131f.23b2..
  Call-ID: 3f39c9310f5f93c56dced2c632df3344@84.100.202.211..CSeq: 102 OPTIONS
  ..Server: OpenSIPS (1.6.3-notls (i386/linux))..Content-Length: 0....       
#