I've attached configurations for a UC520 phone system and Cisco ASA 5510 firewall where the system is colo'd at a data center and no users connect directly to the phone system over the LAN.
Thanks for sharing this, very interesting. How many phones are plugged on the system?
Just found this post and will be stealing as much as I can of it. Looking at hosting some phones remotely, most on site, but also behind an ASA because of all of the tunnel needs.