Telephony Signaling

Cisco CallManager: Understanding Direct-Inward-Dial (DID)

Document ID: 43961

Updated: Feb 29, 2008



Direct-Inward-Dial (DID) is a service offered by telephone companies that enables callers to dial directly into an extension on a PBX and not use an auto-attendant. This document addresses the various DID options supported when you implement a Cisco CallManager solution. This document also offers possible workarounds that employ auto-attendant solutions for customers with Cisco voice cards that do not natively support DID.



Readers of this document should have knowledge of these topics:

Components Used

This document is not restricted to specific software and hardware versions.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.


For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Implement DID in a Cisco CallManager Environment

DID Supported Solutions

Cisco CallManager supports DID on three types of circuits:

Remember that the very design of the VIC-Foreign eXchange Office (FXO) ports do not allow them the ability to interpret inbound signaling; the ports simply go off-hook and either present a dial-tone derived from the gateway, or a private line auto ringdown (PLAR) connection that has been configured to automatically route the call to an extension, operator, or auto-attendant.

DID Alternatives in an FXO Environment: Auto Attendant Options

If only FXO ports are available, "true" DID services from a telephone company can never be utilized. This means that each user that wants a personal DID number requires a dedicated analog phone line, which could be cost-prohibitive.

There are three alternative solutions that allow for internal users to have limited DID functionality, where inbound Public Switched Telephone Network (PSTN) calls are handled by an automated attendant (within Cisco Unity, Cisco CallManager, or certain IOS gateways). Callers are given the option to enter an extension that routes the call directly to the internal user’s phone, or to be routed to a default location, such as an operator.

These three documents provide specific configuration notes to offer this alternative to "true" DID:

Using Translation Patterns

Cisco CallManager translation patterns can be used to map DID numbers to internal extensions.

In this sample configuration, a translation pattern is created to map 10-digit DID numbers to 4-digit internal DNs. The DID numbers range from 408-555-1000 to 408-555-1999, and the corresponding internal extensions range from 1000 to 1999.


In order to map DID numbers to internal extensions, complete these steps:

  1. Go to the Cisco CallManager Administration page. From the menu, choose Route Plan and then Translation Pattern.


  2. Click on Add a New Translation Pattern.


  3. Enter the incoming DID number pattern in the Translation Pattern.

    For example, enter 4085551xxx. Then, choose the appropriate values for Partition and Calling Search Space.

    In order to learn more about partitions and Calling Search Spaces (CSSes), refer to Understanding and Using Partitions and Calling Search Spaces with Cisco CallManager.


  4. Uncheck the Provide Outside Dial Tone checkbox.


  5. Under the Called Party Transformations section, enter the internal extensions pattern for the Called Party Transform Mask. In this example, it is 1xxx.


  6. Click on the Insert button.

Now, the calls to DID numbers 408-555-1000 to 408-555-1999 are mapped to the internal DNs (which range from 1000 to 1999).

Note: When you need to add new DID numbers to the existing system, you need to create a new translation pattern in the Cisco CallManager server.

Note: You can also assign complete DID numbers as an extension on IP phones provided that CallManager receives all the digits of the DID. If you strip the digits at the H.323gateway and send only the last 4 digits, the above method does not work.

Related Information

Updated: Feb 29, 2008
Document ID: 43961