asterisk users - May 2003 - Asterisk codec issue with sip / iax.

Hello,

I am doing some testing with my brother.  We both have asterisk running
with a Cisco 7960 locally and it works great.  Using SIP between the asterisk
boxes works great also.

If I use IAX to call his remote extension, it fails because the remote
asterisk server tries to use GSM to talk to the 7960.  I end up going to
his voicemail, which works fine.

If he calls the same way it has the same issue in my direction.

Apparently, the local asterisk is happy to convert G711 to GSM for transport
over the IAX connection (IAX2 has the same issue apparently), but the remote
asterisk does not convert GSM back to G711 for the remote 7960.

So the flow looks like:

7960 -> G711-SIP -> asterisk -> GSM-IAX -> asterisk -> GSM-SIP
-> 7960

Of course I want the last SIP conversation to be G711.  I have disabled
the GSM codec in sip.conf on both ends since my 7960 phones do not support
it, but apparently the IAX -> SIP process is ignoring that setting?

I wonder if I am just missing some basic configuration settings or if this
is not expected to work?  I don't want to disallow GSM on my IAX connections
since I was hoping to use asterisk to convert the G711 to GSM for WAN
transport.

I have not explicitly configured anything on either end for IAX, I am
just using the 'guest' setup and calling like this:
	exten => 555,1,Dial(IAX/guest@1.2.3.4/1234)

Any help would be appreciated.
Thanks.

-Andrew