Setup NAT on Ubuntu 14.04

гm trying to insert my desktop between an appliance and the rest of the network to монитор the traffic coming off of it due to some security concerns. гd like to setup NAT so that the devices behind my testing NIC appear to be my own desktop to the rest of the network. гve tried the information гve seen around for 10.04, but that doesn't seem to be working.

гd like to stick to ufw схвати much туз is possible because гm trying to learn and become comfortable with the wonders that is ufw, but if it can't handle that, it's умрите.

Your help in configuring this is much appreciated.