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:
This document is not restricted to specific software and hardware
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
Technical Tips Conventions.
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.
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
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:
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
Go to the Cisco CallManager Administration page. From the menu,
choose Route Plan and then Translation
Click on Add a New Translation
Enter the incoming DID number pattern in the Translation
For example, enter 4085551xxx. Then, choose the
appropriate values for Partition and Calling Search
In order to learn more about partitions and Calling Search Spaces
(CSSes), refer to
and Using Partitions and Calling Search Spaces with Cisco
Uncheck the Provide Outside Dial Tone
Under the Called Party Transformations section,
enter the internal extensions pattern for the Called Party Transform
Mask. In this example, it is
Click on the Insert
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.