[Asterisk-Users] Creating a SIP gateway for use behind NAT

[Leif Madsen]

Hi all,

Here is a graphical diagram of what I am trying to do:

<SIP> <---> <GW/NAT/*> <--IAX--> <*> <--TDM400P--> <Analog Phone>

So I have incoming SIP calls go to the * on the GW, which I then want to 
forward over IAX to the second * box behind the NAT GW.  If I was to 
place a call on the second * box, it should then forward to the * on the 
NAT GW and place the call to the SIP destination.  Thus, this should 
create a 2 way communication between the * box BEHIND the NAT GW, and 
end point.

Now, the REASON I am doing this is because the TDM400P card I have is an 
older version, and has a lot of noise on the GW box, but is eliminated 
when using it in the box behind the GW.  I realize I can just get this 
card replaced, but I am just using it on loan from the school, so until 
January comes around, I can't send it back, so this is my work around 
until then.

I have built the IAX registrations between the boxes, so they register 
with each other.  What I am trying to figure out is how to use my 
existing dial plan which worked on the gateway.  This is going to work 
with FWD, so I should be able to receive calls on my 18924 number, and 
the 55555 welcome line as well.

Couple of questions:

1) Should the GW or the second * box register with FWD?
2) Am I basically going to be using a blank configuration on the GW box, 
and having the second * box with all the fancy dial plan stuff, or the 
other way around?
3) Am I looking at using the switch => command?  If so, an example would 
be fantastic, I've looked around on the digum list with google, but 
can't seem to find anything, perhaps I'm just using the wrong search words?

Also, does my logic seem to make sense?  Again, I would have just loved 
to put the TDM400P card in the GW machine, but unfortunately the dd line 
to make the CPU go to 100% just isn't very practical since I would like 
to use it for more than just *.

If I can think if anything else, I will reply to this post.

Thanks in advance for any help or direction,
Leif Madsen.