[cisco-voip] Issue with anonymous calls on a SIP trunk

[Andy]

Hi,
I have an issue with anonymous (callerid witheld) calls on a SIP trunk 
which I can't figure out.

Call comes in over sip trunk via a cube to cucm, if the callerid is know 
then the call gets placed to the dialed number ok.
But if the number is withheld on the inbound call leg their is an 
additional update message which contains the CUCM ip address, but the 
SIP provider is unable to route to this address so one way voice is the 
result.

Does anyone have any idea how to fix this?

-- 
Regards

Andy