In my current setup, I have a NETGEAR Wiressless-N Gigabit router WNR3500NL and a 3COM 10/100 24-pt switch.
The router has 5 ports, a single Internet port(yellow) followed by 4 Ethernet ports(orange) http://i.imgur.com/ObAUN.png
The Internet port(yellow) is connected directly to the Internet, the first Ethernet port is used to connect to a printer, the second Ethernet port is used to connect to an external desktop PC, the third Ethernet port is connected to the switch.
On the switch, the first port is connected to the router, as explained above, while the remaining ports are hooked up by several Ethernet cables.
For example, on my wired desktop. It will go through the following connection.
<<My PC>> -> <<Switch>> -> <<Router>>
As of now, the switch won't make any difference because port redirection works fine out of the box even with the switch in place.
As for wireless users, they would just connect to the router wirelessly via the SSID.
So the question is, I would like to setup a proxy on the external desktop PC that is connected to the router and force both wired/wireless users to go through a proxy first, instead of being able to access the Internet directly.