In a voice network that has CallManagers and H.323 gateways, you need to understand the interaction between the two so that you can properly configure call flow. On the CallManager, you configure a dial plan to send calls to the H.323 gateways when needed. On the H.323 gateways, you configure dial peers to forward calls out of the gateway. You can forward calls to a CallManager using a VoIP dial peer, to the PSTN as a POTS dial peer, to another gateway using a VoIP dial peer, or to directly connected voice ports as POTS dial peers.
You can control the treatment of incoming and outgoing calls with dial peers. In your dial planning, consider the need for such things as number translations or other digit manipulations, or call restrictions. If you are using SRST, be sure the dial plan will work both with and without CallManager.
You need at least one dial peer with a destination pattern to route outgoing calls. Default incoming POTS and VoIP dial peers exist, but you should specifically configure dial peers for incoming calls if you need nondefault services. The default VoIP dial peer includes the following configuration:
The default POTS dial peer includes the following settings:
Because you must configure an H.323 gateway with the information you need to route calls, the configuration can get complex in a large network. You can simplify the configuration by creating a hierarchical structure using gatekeepers and perhaps a directory gatekeeper.
When you use a gatekeeper, the gateway routes all inbound calls to its local network, but it communicates with the gatekeeper for outbound calls to unknown phone numbers. This simplifies the configuration because the gateway does not need to know how to reach every phone number in your network.
Part I: Voice Gateways and Gatekeepers
Gateways and Gatekeepers
Part II: Gateways
Media Gateway Control Protocol
Session Initiation Protocol
Connecting to the PSTN
Connecting to PBXs
Connecting to an IP WAN
Influencing Path Selection
Configuring Class of Restrictions
SRST and MGCP Gateway Fallback
Using Tcl Scripts and VoiceXML
Part III: Gatekeepers
Part IV: IP-to-IP Gateways
Cisco Multiservice IP-to-IP Gateway
Appendix A. Answers to Chapter-Ending Review Questions