CUCM Digit Prefix and Stripping

The Digit Prefix feature prepends digits to a number. Any phone keypad digits from 0 to 9, and the * and # digits, can be prepended to the calling or called numbers.

The Digit Prefix feature can be applied to a calling-party or a called-party number and configured under the corresponding transformation setting in the route-pattern, route-list, or translation-pattern configuration.

Figure 12-6 displays the calling- and called-party prefix configuration available at the route-pattern, route-list, and translation-pattern configuration areas.

Digit discard instructions (DDI) remove parts of the dialed digit string before passing the number on to the adjacent system. A DDI removes a certain portion of the dialed string (for example, when an access code is needed to route the call to the PSTN, but the PSTN switch does not expect that access code).

Digit stripping is configured under the called-party transformations by selecting a DDI. It can be configured at route patterns and at route groups of a route list.

For North American Numbering Plan (NANP) patterns (@), the entire range of DDIs is supported; with [email protected] patterns, only DDIs <None>, NoDigits, and PreDot can be used.

Figure 12-6 Digit Manipulation: Prefix Digits

— Calling Party Transformations-

|j4[Use Calling Party's External Phone Number MasEd

Prefix Digits (Outgoing Calls) | Calling Line ID Presentation* | Default Calling Name Presentation* | Default

— Connected Party Transformations-

Connected Line ID Presentation* |Default Connected Name Presentation* |Default

— Called Party Transformations-

Discard Digits | PreDot IntlAccess IntlDirectDial 3

Prefix Digits (Outgoing Calls) |

For the PreDot DDI to work, the route pattern has to include a period (.) delimiter. DDIs are available at the route-pattern and route-list (route-group link) levels, as shown in Figure 12-6 (discard digits).

Table 12-2 displays different DDIs and how they would apply to a route pattern of [email protected] with some dialed digit examples. An access code with two digits before the @ symbol is not used in most systems, but has been used in the example to illustrate the flexibility of DDIs. The digits that would be discarded appear in bold and are highlighted.

Table 12-2 Digit Discard Instructions


Discarded Digits

Used For


95 1 214 555 1212

Removes access code


95 1 214 555 1212

Removes all digits that are in front of a valid numbering plan pattern

11D/[email protected]

95 1 214 555 1212

Removes PreDot/PreAt digits and local or longdistance area code

[email protected]

95 1 214 555 1212

Removes long-distance identifier


95 011 33 1234 #

Removes international access (011) and country code


95 1010321 1 214 555 1212

Removes carrier access (1010) and following carrier ID code

Trailing #

95 1010321 011 33 1234 #

Removal of # sign for PSTN compatibility


PreDot and NoDigits DDIs are the only DDIs that can be used if the pattern does not contain the @ sign.

NOTE Trailing # is automatically removed by default by CUCM. You can turn off this behavior by changing the Strip # Sign from Called Party Number CM service parameter to False.

Figure 12-7 illustrates a call in which CUCM applies the PreDot DDI to the 9.8XXX route pattern. The access code of 9 is stripped from the dialed digits, and four digits of 8123 are routed to a traditional PBX. The traditional PBX may have a Session Initiation Protocol (SIP) trunk to CUCM, or there may be a gateway between the devices so that a traditional telephony interface can be used to connect the two systems.

Figure 12-7 PreDot Digit Discard Instructions


Figure 12-7 PreDot Digit Discard Instructions


Match: 9.8XXX Discard: PreDot

Called Party: 8123



Figure 12-8 illustrates the PreDot 10-10-Dialing DDI applied to the [email protected] route pattern. This compound DDI strips the access code (9) from the dialed number (91010288 1 214 5551212), removes the carrier selection (1010) and carrier identification code (288), and then sends the 11-digit long-distance phone number 1 214 555-1212 to the gateway device. Removing the 10-10 dialing parameters guarantees that long-distance calls will be billed by the preferred carrier. Most organizations contract minimum guarantees with the longdistance provider of their choice. Although end users might believe that they are saving the company money by routing the call across an advertised carrier, they may be incurring additional costs to the organization. This compound DDI works only if the @ symbol is part of the route pattern. Translation patterns could perform the same functionality without introducing a route pattern with the @ symbol into the dial plan.

Figure 12-8 Compound Digit Discard Instructions



Match: [email protected] Discard: PreDot 10-10-Dialing n

Called Party: 1 214 555-212

User Dials: 9101028812145551212

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  • tobias
    Where is CUCM predot used?
    17 days ago

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