We have an Microsoft Application MOC ( Microsoft Office Communicator ) 2007.

For Voice to work perfect MOC 2007 requires to have an public IP address defined on its interface and it should not be NATTED on the firewall. MOC provides built-in support for external users behind NAT with the open-standard mechanism STUN that enable media streams (Audio and Video) to traverse NATing proxies and firewalls.

The VOICE doesnt connect behind a NATing Firewall. BUT External users with Public IP addresses can participate in Audio and Video sessions without any issue.

Firewall is ASA 5500 Series

Help would be appreicated.

Thanks