3.6 Implementing Site Codes for On-Net Calls

This topic describes how to use site codes for on-net calls.

Users dial access and site codes, followed by the directory number. Directory numbers do not have to be unique across sites because of site identification.

In the example, two sites have overlapping and nonconsecutive directory numbers. To accommodate unique addressing of all endpoints, site-code dialing is used. Users dial an access code (8, in this example), followed by a three-digit site code. When calling the phone with directory number 1001 at the remote site, a user who is located at the main site must dial 8222.1001. For calls in the other direction, remote users dial 8111-1001. When distributed call processing is used, each Cisco Unified Communications Manager cluster is aware of only its own directory numbers in detail. For all directory numbers that are located at the other site, the call is routed to a Cisco Unified Communications Manager server at the other site based on the dialed site code.

Digit Manipulation Requirements for Using Access and Site Codes

The figure shows digit manipulation requirements for site code implementation.

When you use site codes in multisite environments with distributed call processing, call processors must add or strip access and site codes from the called and calling numbers, as needed. In the example shown in the figure, the dial plan is designed so that both the called-party and calling-party numbers include access and site codes when they are sent over a trunk.

You can implement such a dial plan by adding the access and site codes to the calling-party number at the originating cluster on the outbound trunk. At the receiving cluster, on the inbound trunk, you strip the access and site codes from the called-party number.

Regarding call routing, you can either configure a route pattern per destination site, or you can use GPDR orCCD to advertise the patterns.

Access and Site Codes in Centralized Call-Processing Deployments

If overlapping directory numbers exist in a centralized call-processing deployment, access and site codes are implemented in a different way, as shown in the figure.

The example shows two sites with centralized call processing. Directory numbers in the main site (“headquarters,” or “HQ” in the figure) and the remote site (“branch,” or “BR” in the figure) partially overlap. Access and site codes are used to solve the problem of overlapping directory numbers.

In the example, partitions and CSSs can be deployed so that phones at the remote site do not see the directory numbers of phones that are located at the main site, and vice versa. Then a translation pattern is added per site.

The translation pattern of each site includes the access and site codes of the respective site. Phones at each site have a CSS assigned, which provides access to the directory numbers of the local site and the translation pattern for the other site or sites. The translation patterns are configured with a transformation mask that strips off the access code and site code. Further, each translation pattern must have a CSS, which provides access to only those directory numbers that are located at the target site of the respective translation pattern. This way, all phones can dial local directory numbers and site-code translation patterns for accessing other sites. After a user dials an intersite number (composed of the access code, site code, and directory number), the corresponding translation pattern is matched. The translation pattern strips the site code and access code so that only the directory number remains. This directory number is matched again in the call-routing table using a CSS that has access only to the directory numbers of the site, which was identified by the site code.

An alternative to a solution with translation patterns is the use of the enterprise alternate number, which you can configure on the Directory Number configuration page. As indicated in the name, the enterprise alternate number is an alternate number for the configured directory number in the format that is used for enterprise-wide dialing. In the example, where intersite dialing is done by dialing 8, followed by a 3-digit site code, followed by the 4-digit directory number, you would configure an enterprise alternate number mask of 8111XXXX at all HQ directory numbers and an enterprise alternate number mask of 8222XXXX at all BR directory numbers. The resulting enterprise alternate numbers are similar to aliases for the directory number. While you must add the directory numbers to a site-specific partition, you will make the enterprise alternate number reachable to all phones by adding it into an enterprise-wide partition.

The enterprise alternate number was introduced in Cisco Unified Communications Manager Release 10