Core Issue
By default, the IPVC gateway listens to TCP port 1820. In Cisco CallManager H.323, gateways are configured to signal through TCP to port 1720.
Resolution
This problem is resolved by changing the signal port of the video conferencing H.323 gateway to 1820.
This can be configured through the Cisco CallManager Administration page. Go to Device > Gateway > Add New Gateway. Select the H.323 gateway and click Next. In the Gateway Configuration page, change the signaling port to 1820. The default value for signaling port is 1720.
