We have a location with one Centrex line coming into an FXO port. There is a fax machine that will be using this line, and they will also be using this for 911 calls only since that is the only line at that location. How would I go about configuring the FXS port for the fax machine to plug into? I have already created the DN for the DID but wasn't sure if there was anything else I need to watch out for..fax
You're best off just configuring the FXS port locally on the router and not forcing the call through CUCM. If you push it through CUCM you'll need to deal with protocol interop and avoiding MTPs to get faxing working reliably. They wrote a whole book on this topic and the answer depends on CUCM version and protocols in play.
If it's locally patched on the router it can just pass through the backplane and be much more simplistic. Build a dial-peer for the fax DID that has the FXS port on it directly and ensure that get chosen.