Today, two different people at completely different times (and for different reasons) noticed the "extra" dust collection point of my router table. It has been there for over 3 years! as one of the first things I did to that table after adding the router plate to it, while in the temporary building.
I guess it's because it's not an every time use thing? I mostly use the opening on the fence of that particular router table, but there is an under table connection on the router itself too. (Triton router)
The port I am referring to though is out in front of the router plate, directly in line with the bit centerline. It's just a simple hole that accepts a hose fitting. I only use it when doing grooves, like cabinet backs, or huge rabbets (today's project).
When you make a cut like that, the fence extraction point is useless, and the one in the router base prety much is too, though it will get some of it. The main bulk of the dust goes directly out in front of the part you are cutting. So drilling a big hole out there will catch most od the dust.
The first guy noticed it when he saw me connecting two hoses together. (the one for that fitting is always under the table, just not connected to the CT. The second one noticed it when he was watching me work. He saw the uncaptured dust shoot out at the beginning of the cut, then as the part was advancing, the dust was sucked back into the groove and down the hose. He was shocked, never seen such a thing.

I was doing a big rabbet on both edges of a lot of panels. 3/8" high and 2 1/2" wide. That is a lot of dust, especially when your extractor catches most of it. I actually filled m CT26, solid like a brick, twice in the same day. Never done that before. I think I have only filled it completely in a week once or twice?
I started with one that was probably about 1/2 full. Filled it, swapped in a new one, thinking I would be good for the rest of that job at least....nope. It quit again a while later, solid again.

pics
1 the hole in the table
2 the bags in the bin
3 one of the panels

Interesting.  I haven't seen anyone put it in the table.  Usually it's a big gulp at the end.

I put the dust collection inside the fence which is fashioned like a large U-Chanel and closed at both ends.  Dust collection is from the top, but from either end would work too.

It is a very crude fence and a “consumable”, but it works well.  I adjust and then use regular clamps to hold in place.

My first router “table” was a sheet of plywood over two saw horses.  I used it outdoors, so though my current setup is crude, it is vastly more sophisticated than my old one. 

The fence back then was a long L-shaped piece made of 3/4” plywood and it also was clamped to the table with regular c-clamps.

Nice idea.  What about using something like incra magnolock cleansweep?  Don't know how i feel about drilling a hole in my cast iron table

Incra has a similar design that's built in their magnalock rings.   

Incra has a similar design that's built in their magnalock rings.   

The Kreg plate has inserts that you can change (for bit clearance). You could use the largest one in a case like this, which is what I did before this occurred to me, but it depends on the under-table collection source.
Years ago, I had a box around the router, with the hose plugged into it. Later I switched to the port the is built into the side of the Triton router, when I up-graded to that.
Neither of these methods/systems works as well as that hole out front. The initial contact of the bit to the leading edge of the wood is un-shrouded and the forward velocity is quite intense. The downward draw right by the bit cannot catch it at that speed.
It's really interesting to watch this work. It does miss some of the initial chips too, but when the part moves up to where it is laying on the table, some of it gets sucked back through the groove.
I have thought about trying to improve it, maybe with a removable brush? Something that could stick up a little to stop more debris, but have clearance behind the bristles, so they could be pushed backas the board passes over them? I've also considered using an actual vacuum fitting/nozzle with a wider shape than the simple circle, but bigger might kill some airspeed? which might go against the goal?
I don't know, it's not like it's a big deal. It works well now.