Multisite Dial Plan Overview

The following dial plan solutions exist for multisite deployments for centralized call processing:

• Access and site codes: By adding an access code and a site code to directory numbers of remote locations, you can do call routing based on the site code instead of directory numbers. As a result, directory numbers do not have to be globally unique, although they do need to be unique within a site. Configuration requires route patterns, translation patterns, partitions, and Calling Search Spaces (CSS). Adding access and site codes simplifies internal dialing for users in a multisite environment.

• Implementing PSTN access: PSTN access within a CUCM cluster is implemented using route patterns, route lists, route groups, and partitions and CSSs. When implementing TEHO, the same dial plan configuration elements are used; however, more entities have to be configured, which makes the configuration more complex. TEHO reduces the operating cost of long-distance or international dialing.

• Implementing PSTN backup: The IP WAN used in a multisite deployment with centralized call processing is backed up by Media Gateway Control Protocol (MGCP) fallback, Cisco Unified Survivable Remote Site Telephony (SRST), or CUCM Express in SRST mode, and Call Forward Unregistered (CFUR). PSTN backup ensures that calls will go through the PSTN in the event of a WAN link failure.