[Serusers] proxy + nat in the same box

[Klaus Darilion]

Eduard San Anselmo Mateu wrote:
> Hello everyone.
> 
> I have read lots of posts to this list and whitepapers about NAT traversal with
> SIP, but all of them refer to the same problem: the endpoint is behind a nat box
> and SER is after that box. My question is regarding the situation in which SER
> resides at the same box than NAT. Here's a diagram (sorry for that awful
> ascii-art, never been a good artist):
>     _____        ______                      ______         _____
>    |     |      |      |                    |      |       |     |
>    |  A  |------| FW   |-----  INTERNET ----|      |-------|  B  |
>    |_____|      | NAT  |                    | NAT  |       |_____|
>                 | SER  |                    |      |
> 192.168.0.90    |______| IPpA          IPpB |______|       10.0.0.70
> 
> IPpA and IPpB are the public IP addresses of A and B, respectively. SER is
> listening on its private IP. Of course, the SER box also has an RTP proxy.
> 

Why is ser listening on the private IP? Bind ser to the public IP (IPpA) 
and configure the Clients to use IPpA as proxy address.

klaus


> I think there's no problem with RTP, because nathelper's exported functions can
> deal with the problem of changing SDP's fields. My problem has to deal with SIP,
> specially when B invites A into a conversation, and A has to give an answer. In
> that case, when SER has to repeat that answer to B, what will it write in the
> Record-Route header field? It should write IPpA so that B can get to SER in the
> future, but if SER's listening on its private IP, I'm afraid it will write that
> public IP in Record-Route.
> 
> Can anybody please point me in the right direction, or at least address me to a
> place where all this may be explained (not the RFC, please!)?.
> 
> Thanks in advance.
> 
> Eduard San Anselmo
> 
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