Restricted NAP UPnP and audio problems

[Diego]

I have a shared connection behind an ADSL modem/router,
UPnP enabled (speedtouch 510, firmware 4.2. -latest one-)
and then an Asus WL-500 router (The modem only has one
output, so I installed the Router to provided multiple PC
connectivity + wireless connectivity), which is UPnP
enabled (latest firmware too).

With the original firmware of the Asus router, Messenger
6.2. saw "a Cascaded UPnP Symmetric NAT" and didn't
provide Audio. After upgrading the router, The connection
information provided by messenger has become "Cascaded
UPnP Port Restricted NAT ". I've read somewhere on the
internet that such a config. should work ( and indeed,
when I try to connect, the system does not issue the
warning telling me that the connection might not work).

Any hints as to configure it?
Does this configuration limit somehow the way the other
party can be connected so as to successfully contact via
audio?

Thanks for any useful info.

 

[Diego]

Forgot to mention, for completeness, I have F-Secure 5.52
firewall, but I've tried with and without it activated. It
doesn't change anything...

 

[Diego]

More to it. While videoconferencing , works fine (both
audio and video) Audio alone does not go through. In this
case, my contact hada a a Cascaded UPnP IP restricted NAT"

I suppose this is a definitve hint for somebody knowing
what's behind the scenes in messenger...