Digit Manipulation

Digit Manipulation
Digit manipulation is closely connected with call routing and path selection. For inbound
calls, the called number needs to be modified to match internally used patterns. For
example, a call from the PSTN might use the DID number 4085552001, but the internal
pattern is 2001. Thus, the leading 408555 needs to be removed to successfully route a
call. Also, the inbound calling number should be dialable—for example, using the missed
calls directory. This would include prefixing a 9 to the calling number of inbound PSTN
calls.
For outbound calls, digit manipulation ensures that the calling and called party numbers
match specific requirements. For example, the PSTN access code 9, which is typically
used in telephony environments, needs to be stripped from the called number when sending
a call to the PSTN.
Several commands and configurations are available on Cisco IOS gateways to perform
digit manipulation depending on the scenario. In general, plain old telephone service
(POTS) dial peers support a wider range of commands for simple digit stripping and prefixing,
whereas VoIP dial peers are primarily dependent on voice translation profiles.