If you are not using Direct Inward Dialing Services also check (for SIP trunks) the "SIP Peer Profile Assignment by Incoming DID" and "SIP Peer Profile Called Party Inward Dialing Modification" forms (values defined in "Inward Dialing Modification" form). Also have a look at System Speed Calls form if there is any mapping.
It is also possible that the carrier is sending numbers that match the internal extensions already, then no modification is needed, you can find out by issuing CCS TRACE ENABLE CONTINUOUS command or SIP TCPDUMP ON (for SIP trunk only) and analyze the pcap file in WireShark. I hope it helped.
I checked the above forms but I did not find any mapping of an internal extension to an external number. Also, the internal extension number is not part of the external number i.e. the last four digits of the external number do not match the four digit internal extension number, even though dialing this external number will ring the internal extension.
However, I ended up finding the mapping. It was added to Keys tab under the
User and Services Configuration form with the following settings:
Line Type: Single Line
Button Dir. Number: (last four digits of the external number entered here) e.g. 1234
Ring Type: Ring
The number entered under Button Dir. Number was also added to the
Multiline Appearance Groups form with the following settings:
Group Directory Number: (last four digits of the external number entered here) e.g. 1234
Group Type: single line
The last four digits of the external number (1234) have also been added to the
Call Rerouting form, but are not rerouted to another number.
Using the maintenance command
LOCATE NUMBER 1234 tells me that this number is a
Non Prime Broadcast Group.
I have noticed that the Multiline Appearance Groups form contains numerous other Non Prime Broadcast Group numbers. How can I find out which of these Non Prime Broadcast Group numbers have been provided by the service provider, so that I can map them to other extensions so that they can receive external calls directly?