Most router tables allow you to capture dust and chips from the top of the table through a collection port on the fence, but this is only effective for some operations. Other operations require dust collection from the bottom of the table. There are a few different methods to do this with varying levels of effectiveness; usually they involve encasing the router in some sort of vacuum box.
Keen Products’ dust collection system collects dust right from the point of entry on the bottom of the table, leaving your router accessible and open so it won’t overheat. It also removes most of the dust before it has a chance to fall into the router motor, hopefully prolonging its life.
The dust collection system hooks up to a 2-1/2″ hose and splits the suction between a top-mounted port and the dust cup which surrounds the lower part of the bit and collet. I’d be careful purchasing this if you use a router lift though — one of the reviewers on Woodcraft’s site said this interfered with his router lift so he could not change bits from the top side of the router table.
The Dust Collection Kit comes with the rubber boot, hose, splitter, and several adapters to fit the dust collection port on your fence. The best price I could find for this dust collection kit was $35, plus $8 shipping from Infinity Tools.