CUCM Advanced Route Plan: Using Digit Transformations

The dial plan of a VoIP system can be much MORE complex than that of the traditional PBX realm since a call can move in multiple directions (such as WAN and/or PSTN). In this Nugget, Jeremy discusses a failover situation where calls can transparently move from the WAN to the PSTN without user intervention. To do this, you’ll learn about Calling and Called Party Transformations (such as discard digits, transformation masks, and prefix digits).


  • Can be applied at a Route Pattern level… instantly change the digits before the number is dialed
  • Can be applied at a Route List to Route Group level.. (To change a WAN dial plan to PSTN friendly/compatible digits)

Called Party Transformations

  1. Digit Discard Instructions (Predot for example – Jeremy used in production only, nothing else)
  2. Prefix Digits
  3. Called Party Transform Mask

Calling Party Transformations

  1. Calling ID/Name Presentation
  2. Prefix Digits
  3. Calling Party Transform Mask

Under the Line/DN itself…’External Phone Number Mask’ = 01376 5xxxxx for an extension of 31298 for example.
Then on the Route Pattern tick the box to enable the External Phone Number Mask on the Line/DN