Which discard digits instruction removes all digits prior to the North American Numbering Plan portion of the route pattern?
A. PreDot
B. PreAt
C. Pre
D. PreNANP
Which discard digits instruction removes all digits prior to the North American Numbering Plan portion of the route pattern?
B is Correct
https://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/4_0_1/ccmsys/a03rp.html
Using Wildcard Characters in Route Patterns
Using the @ wildcard character in a route pattern provides a single route pattern to match all NANP numbers, and requires additional consideration.
The number 92578912 matches both of the following route patterns: 9.@ and 9.XXXXXXX. Even though both these route patterns seem to equally match the address, the 9.@ route pattern actually provides the closest match. The @ wildcard character encompasses many different route patterns, and one of those route patterns is [2-9][02-9]XXXXX. Because the number 2578912 more closely matches [2-9][02-9]XXXXX than it does XXXXXXX, the 9.@ route pattern provides the closest match for routing.
When configuring route patterns, take the following considerations into account:
•When @ is used in a routing pattern, the system recognizes octothorpe (#) automatically as an end-of-dialing character for international calls. For routing patterns that do not use @, you must include the # in the routing pattern to be able to use the # character to signal the end of dialing.
•If the route pattern contains an at symbol (@), the Discard Digits field can specify any discard digits instructions (DDIs).
The “Special Characters and Settings” section lists DDIs and describes the effects of applying each DDI to a dialed number.
Discard Digits Instructions
A discard digits instruction (DDI) removes a portion of the dialed digit string before passing the number on to the adjacent system. Portions of the digit string must be removed, for example, when an external access code is needed to route the call to the PSTN, but the PSTN switch does not expect that access code.