The vent for a 2" trap can be up to 5 feet away from the trap and be legal. The drain that's there now (hopefully) has a vent tied to it somewhere...what he means is that with any luck it's within ONE foot of the current location, so moving the drain would be as simple as...cutting the existing pipe somewhere then: original---coupler---4 feet of pipe---coupler---original. As long as you're draining 1/4" per foot of run, you're good. You need to find out where the existing vent is first.
What Ron means is that if you have a 2" drain trap it must be vented within 5' of the trap. A vent is a way of getting air into the drain line so it drains properly. They can be a pipe running through the roof or an air admittance valve. These can be place in the basement and only allow air to come into the pipe and will close if water hits it.
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