asterisk users - Dec 2006 - GXP-2000 and Asterisk Configuration

Hello,

We are having a hard time making the GXP-2000 work reliably with Asterisk.
We have several clients using the GXP-2000. These phones are behing NAT
and our Asterisk server has a public IP (no NAT).

The biggest problem we face is the clients complain of random, but
frequent, calls (in or out) where there is no audio.

We have enabled STUN on the phones and when we do a "sip show peer X",
we
see that the Addr->IP and Reg. Contact fields both have the public IP of
each respective client. When we do a "sip debug peer X", we notice
that
Asterisk displays Warning: 399 207.XXX.XXX.XXX "detected NAT type is
symmetric NAT". We also noticed that some of our other clients show a
different debug information Warning: 399 72.XXX.XXX.XXX "detected NAT type
is port restricted cone". Even worse, for some for example, one client
that has multiple GXP-2000, some of them report the NAT as being symmetric
and some report it as being port restricted.

The phones are Grandstream GXP2000 1.1.1.14 and we are running Asterisk
1.2.13.

What should be the proper setting in Asterisk for the nat option in the
sip peer?
What should be the proper settings in the GXP-2000 phone itself?

I was recommended on the list that I use nat=route and to disable the STUN
server on the GXP-2000. However, even though that seemed to work at first,
it still presented the problem of calls with no audio.

Thanks