The dust collection cabinet is a bit of a temporary hack as long term I want to build a proper cabinet under the table to store bits in etc, so please don't judge me - images as requested for illustration only!
This is my table. It's a piece of 6mm steel plate which replaced the sheet steel extension on the right of my table saw. It's supported underneath by 40mm aluminium profile with some support legs, and the support legs and saw are all carried by a box section steel frame on four casters to move about the workshop. I chose steel because I wanted a magnetic table top for MagSwitch clamps and featherboards, which is a decision I'm really happy with. When used as a router table, I secure my fence (Incra LS positioner) to the mitre slot of the table saw with two T bolts (to the right of the picture).
A close-up of the router plate. Again, it's 6mm steel, so sits perfectly level on supports flush to the underside of the table. My most commonly used insert ring is installed, a 32mm - these are made from 3mm Perspex and secured to the plate by two countersunk machine screws. The dust extraction slots were routed into the insert using a 10mm bit and trammel jig before trimming the insert down to size.
A view of the dust collection cabinet from the rear. You can just make out the 100mm elbow for connection to the extractor. In the foreground is a 63mm hose which is permanently installed, this goes to the fence and is simply connected at the fence end when using the table. All built in 18mm MDF (in a hurry!). The thing with a wire in the foreground is a resistor - I have a number of these connected under the saw and extension tables to a 12V lighting transformer, which I switch on in the winter to avoid condensation and corrosion of the table.
Front view of the router's dust collection cabinet, door closed. Held shut by a couple of tabs which spin around the mounting bolt.
And with the door open, showing the router inside and the rebate in the cabinet with foam weather strip to form a seal. There is a 240V socket inside the cabinet which is switched by an NVR switch mounted under the table.