[Asterisk-Users] Restricting/Negotiating H323 Port Ranges

[woody+asterisk at solutionsfirst.com.au]

Our VoIP provider wants to use a restricted set of ports for H323.  All
their current users have hardware at the customer premises which does this
successfully for them.

We are trying to set up Asterisk to do the same (with their co-operation).

I am not familiar with the H323 terms for these connections, so bear with
me...

The (Connect/Listen) Port is 1720 (set in (o)h323.conf)
Tcp Range 10000-50000 (set in oh323.conf or rtp.conf)
Udp Range 10000-50000 (set in oh323.conf or rtp.conf)

Now my tcp dump shows this with oh323 when I try to make a call to
number at provider:

Connect from high range port (10006) to provider 1720
They have a few exchanges....

Then asterisk connects from port 10007 to provider:2033

My provider wants this to be port 2020 all the time, but the port number
just keeps increasing by one.

So the next call will involve a port of 2034 at their end.

Is there somewhere in either channel to restrict this middle port range to
just 2020?

Or is there some negotiation which asterisk/openh323 libraries don't do?

Cheers,
Woody