Uri Dialing And Firewall Traversal - Cisco TelePresence Administrator's Manual

Dial plan and call processing

URI dialing and firewall traversal

If URI dialing via DNS is being used in conjunction with firewall traversal, DNS zones should be configured
on the VCS Expressway and any VCSs on the public network only. VCSs behind the firewall should not have
any DNS zones configured. This will ensure that any outgoing URI calls made by endpoints registered with
the VCS will be routed through the VCS Expressway.
In addition, the DNS records for incoming calls should be configured with the address of the VCS
Expressway as the authoritative gatekeeper/proxy for the enterprise (the DNS configuration examples
section for more information). This ensures that incoming calls placed using URI dialing enter the enterprise
through the VCS Expressway, allowing successful traversal of the firewall.
Cisco VCS Administrator Guide (X7.2) Page 204 of 498