Core Issue
The user is unable to make external calls. When attempting to dial out, a fast busy signal is recieved. All internal calls work fine and the Cisco CallManager server has dual network interface cards (NICs) enabled on it.
Resolution
This problem is due to both NICs being enabled on the Cisco CallManager server at the same time. This is not a recommended configuration.
Dual NIC cards are not supported. The recommendation is to have two NICs and use one as fault tolerance, but only one is operational at a time. Failing to disable the second NIC may result in two IP addresses being assigned to the Cisco CallManager server. Assigning two IP addresses to the Cisco CallManager server may cause a loss of service.
Installing the Cisco Media Convergence Server Network Teaming Driver discusses dual NIC teaming. Disabling one of them helps resolve this issue.
