Cisco CallManager Discard Digits Instructions DDI

Discard Digit Instructions -or DDI- are a set of commands you can apply to a called party number. Usually, DDI are applied to route patterns that include the @ wildcard. However, you still can apply them to route patterns that contain the “.” wildcard. In addition, using DDI is relative to a numbering plan. So in CUCM, by default if you are going to use the various instructions provided with DDI, you are applying them to the North American dial plan.
DDI is the first set of called party transformations that is executed, followed by the Called Party Transform Mask and Prefix Digits.

Configuring Discard Digits at the route pattern level

  • Go to Call Routing –> Route/Hunt –> Route Pattern
  • Click on Find to list all available route patterns
  • click on the route pattern for which you’d like to add Discard Digit instructions
  • Under Called Party Transformations, you will find the Discard Digits menu


As you can see on the screenshot, there are a lot of options in the Discard Digits feature. The most common one I know is the “Predot” instruction:


Configuring Discard Digits at the Route list detail level

The same types of discard digits instructions seen at route patterns are available at the Route list details level.

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Result of applying Discard Digits at route pattern and at route list details

This table summarizes the impact of Discard Digits when applied at route patterns and at route list details level.


Discard Digits value at route pattern, Discard Digits value at RouteList/RouteGroup, Result







Configuring Discard Digits in translation patterns

Let’s see first if the Discard Digits feature is supported on translation patterns:

  • Go to Call Routing –> Translation Pattern
  • Click on Find to list all available translation patterns
  • click on the translation pattern for which you’d like to add Discard Digit instructions
  • Under Called Party Transformations, you will find the Discard Digits menu.


However, it is greyed out. This does not mean that Discard Digits is not supported with translation pattern. But, it’s simply because we are not using a @-based translation pattern.

When we check in the upper part of the translation pattern page, we have the Numbering Plan greyed out too:


As soon as we insert a @ wildcard, anywhere in the pattern, both Numbering Plan and Discard Digits become available:



For more information in discard digit instructions, visit this link.

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