We are in process of changing our carrier for voice and data. We are going from a carrier that is sending both down a single T1 to an IAD and the crossing to our 2821 and going from there. We need to connect to our new voice carrier via SIP. How would I go about setting up a trunk in the CallManager or do I need to do something on my 2821 to connect the SIP from the provider to my CallManager?
You can point your callmanager directly to your new SIP SP. Create a SIP trunk Callmanager and configure its destination ip address to your SIP SP, this is the most simple way, but this version has lots of limitation on SIP trunk and additional configuration may required if you don't want to expose your CUCM directly to the SIP SP.