AsteriskNOW + OpenSER

Hi!

SCENARIO:
A campus LAN with an Asterisk PBX (AsteriskNOW) and a SIP server (OpenSer using Radius). In the actual configuration, Asterisk users (defined in /etc/asterisk/users.conf) can talk to each other and the same stands for users directly connected to SER.

Keeping the two databases separate, I want to allow phone calls like:
“the user with extension 6000 connected to Asterisk make a phone call to the user foo@ser and viceversa”.

I’ve seen this
tutorial, but it refers to the integration of the two databases.

I just want a sort create a transparent gateway between the two systems. How can I do this?