I agree with Steve. I would definitely prefer real Cresnet, but in your situation I wouldn't hesitate to use the CAT, esp. with Keypads.
I did a retro project 12+ years ago where I had (10) TPS-6L panels with only (1) cat5e at each. I used Cat-to-Terminal adapters for the connections on both sides and it has worked flawlessly since then. We're in the process of upgrading the system to TSW panels so we'll now convert the CAT back to network connections!!
***? Because Category cables are not intended, with their small solid core conductors, to be stripped, twisted and screwed down upon (maybe this is why some have issues), I HIGHLY recommend RJ45 to Terminal strip adapters.
This is a bit of a pain, but it's definitely much better than re-wiring in some retro projects...
Here's an example of one that I've used:
HTH, Chris K
