Hi,
if you're talking about Cisco UCS, I suggest you deployed Cisco UCM.
In that case you probably don't need to sniff the traffic to record Cisco UCM calls. You can try BiB recording supported by the most of Cisco IP phones.
But you do need SPAN/RSPAN to record low-cost Cisco IP phones or 3rd party SIP devices. If this is the case I think you'd better ask vendor of your call recording solution - they must have Cisco UCS deployment experience.