We are currently deploying a CCM 4.2 system. Each of our offices has an FXS port for paging. We placed a standard phone on the line and used it to call a local extention and it works fine. When we try to call to our corporate office, they can hear me but I can't hear them. This FXS card is in a 2801 that is being used as our firewall and has a VPN tunnel back to our corporate office. The FXS card is registering with an IP address of the tunnel. Could this be causing our issue?