To test NAT traversal is not an easy task. You can test with some friends behind the Internet calling your server on a public IP address. For a test bench the easiest setup is to have two IP phones behind two NAT devices.

Step 1: Copy the openser.mediaproxy script to /etc/openser/openser.cfg:

cd /etc/openser
wget 
http://www.asteriskguide.com/openser/openser.mediaproxy
cp openser.mediaproxy openser.cfg

Step 2: Dowload and decompress the MediaProxy server from AG Projects to the directory /usr/src.

cd /usr/arc
wget 
http://mediaproxy.ag-projects.com/mediaproxy-1.8.2.tar.gz
tar –xzvf mediaproxy-1.8.2.tar.gz

Step 3: Install python if it is not already installed:

apt-get install python

Step 4: Edit mediaproxy.ini according to step 4 of the earlier section Installing MediaProxy.

vi mediaproxy.ini

Step 5: Start the mediaproxy process.

./mediaproxy.py 

Step 6: Assemble you lab bench and register phones 1000 and 1001 behind...