If you are planning to use MGCP gateways in the IPT network, you have to enter the router/switch host name in CallManager while configuring the MGCP gateway. If the router/switch is configured with the domain name (by using the ip domain-name word command), you must configure the fully qualified domain name (FQDN) in CallManager instead of just the host name. For example, if your router/switch host name is 3745-GW and you configured the domain name as xyz.com (using the ip domain-name xyz.com command on the router/switch), then, in CallManager, when you are configuring the gateway, you should use 3745-GW.xyz.com as the MGCP domain name. In this case, CallManager needs to contact the DNS server to resolve the 3745-GW.xyz.com name to an IP address. You can get away without using the DNS name by configuring the static name resolution entry in the HOSTS file. However, in a network with a large number of gateways, this becomes a tedious task.
What is MGCP?
Short for Media Gateway Control Protocol, developed by Telcordia and Level 3 Communications, a control and signal standards to compete with the older H.323 standard for the conversion of audio signals carried on telephone circuits (PSTN ) to data packets carried over the Internet or other packet networks.
The reason new standards are being developed is because of the growing popularity of Voice over IP (VoIP ). Regular phones are relatively inexpensive because they don't need to be complex; they are fixed to a specific switch at a central switching location. IP phones and devices, on the other hand, are not fixed to a specific switch, so they must contain processors that enable them to function and be intelligent on their own, independent from a central switching location. This makes the terminal (phone or device) more complex, and therefore, more expensive. The MGCP is meant to simplify standards for this new technology by eliminating the need for complex, processor-intense IP telephony devices, thus simplifying and lowering the cost of these terminals.