You can either use nathelper or mediaproxy. Check the documentation on these two modules. There are good explanation on why/how.
-----Original Message----- From: serusers-bounces@iptel.org [mailto:serusers-bounces@lists.iptel.org] On Behalf Of Michael Shuler Sent: Wednesday, August 25, 2004 7:44 AM To: 'Michael Shuler'; serusers@lists.iptel.org Subject: RE: [Serusers] NAT
Anyone have an explanation or did this email miss the list?
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Michael Shuler, C.E.O. BitWise Systems, Inc. 682 High Point Lane East Peoria, IL 61611 Office: (217) 585-0357 Cell: (309) 657-6365 Fax: (309) 213-3500 E-Mail: mike@bwsys.net Customer Service: (877) 976-0711
-----Original Message----- From: serusers-bounces@lists.iptel.org [mailto:serusers-bounces@lists.iptel.org] On Behalf Of Michael Shuler Sent: Tuesday, August 24, 2004 5:50 PM To: serusers@lists.iptel.org Subject: [Serusers] NAT
I'm trying to understand the NAT process, can someone tell me if this is correct
Here is my original INVITE from client IP 123.123.123.123 which is received from port 5002 (because its behind a NAT router):
INVITE sip:2175850357@sip2.bwsys.net;user=phone SIP/2.0 Via: SIP/2.0/UDP 192.168.100.2:5060;branch=z9hG4bK-4qxhdyvuyz6t;rport From: "Mike's Springfield snom 1" sip:MikeSnom1@sip2.bwsys.net;tag=k91lt5ydem To: sip:2175850357@sip2.bwsys.net;user=phone Call-ID: 3c275253ad55-krb7eduyhd2m@192-168-100-2 CSeq: 1 INVITE Max-Forwards: 70 Contact: sip:MikeSnom1@192.168.100.2:5060;line=rygvn8mw P-Key-Flags: keys="3" User-Agent: snom200-3.42 Accept-Language: en Accept: application/sdp Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE, PRACK, MESSAGE, INFO Allow-Events: talk, hold, refer Supported: timer, 100rel, replaces Session-Expires: 3600 Content-Type: application/sdp Content-Length: 256
v=0 o=root 20147217 20147217 IN IP4 192.168.100.2 s=call c=IN IP4 192.168.100.2 t=0 0 m=audio 10048 RTP/AVP 18 0 8 101 a=rtpmap:18 g729/8000 a=rtpmap:0 pcmu/8000 a=rtpmap:8 pcma/8000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=sendrecv
Now this invite is going to get forwarded to my TNT (with a public IP) which has SIP capabilities and hands of PRI to a phone switch. So to make NAT support work what would this message look like after being proxied and NAT "adjusted" and what function in SER would be needed to make the changes happen?
Now I know the proxy should be able to learn the port that the INVITE comes in on and can send SIP messages back via the learned port, but I do not understand how the RTP stream works when NAT is involved. My guess is that anything what says 192.168.100.2 (the NAT'ed IP) needs to get changed to the proxy's public IP of 198.88.216.87:5060. This would include the Via and Contact. Now the SDP "c" line has to be changed because it says 192.168.100.2 but it should be changed to 123.123.123.123 (the clients learned IP). Now that leaves us to the problem of the RTP port. The client says it wants to receive on 10048, but how does the generic NAT router know that the snom wants this port opened?
Michael Shuler, C.E.O. BitWise Systems, Inc. 682 High Point Lane East Peoria, IL 61611 Office: (217) 585-0357 Cell: (309) 657-6365 Fax: (309) 213-3500 E-Mail: mike@bwsys.net Customer Service: (877) 976-0711
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