CUCM - call forwarding via Directory Number, retaining original callers number

[icemoom]

Wonder if anyone can help, we need to temporary forward a large number of our users to an alternative external phone number, I can setup a forward against their Directory Number which forwards fine but the incoming call displayed on the receiving end does not display the original callers number, is there anyway of retaining this number and passing it through? The incoming call number displayed is the same for all forwarded calls no matter the DN it's forwarded from or the caller (I assume some system level default outgoing number), this makes it impossible for the receiving end to caller ID any incoming calls. Telephony and specifically CUCM is unfortunately not something I have dealt with much in the past so my knowledge is limited.

[Roger Kallberg]

Can you please check if you’re passing redirecting number information to your PSTN provider for the forwarded calls?

[icemoom]

Apologies but where would I check this? With CUCM or with our provider? Btw we are using SIP if that makes any difference.

[Roger Kallberg]

You would check this on the SIP trunk between CM and your voice gateway as you say you use SIP. Assuming that you would mean the protocol used for the connection to/from CM.

[TONY SMITH]

If you have a CUBE gateway then a debug there will show the call legs both to CUCM and to the provider.
"debug ccsip messages"
What does the final called party see as the calling number? Is it the DDI of the call forwarded extension, or the pilot number, or something else?