1. I don’t think I would attempt something like…
It just plain too complicated. To set the record straight… Most of the networks we’ve (Dux Computer Works) built were for small businesses. Except for one case, I do not we believe we have built a network with a diameter that was greater than 100 meters. The one I do recall was installed quite a few years ago and used 10BASE5 (thickwire coax) Ethernet to overcome distance limitations. The maximum length for a 10BASE5 network is 500 meters (hope I got that one right). Why are you limiting the MODEM leg to 10 feet?
2. Most routers are a combination of a NAT and a switch.
3. I’ll defer to Charles Spurgeon on that question, question 5, and the specifics of question 1. http://www.ethermanage.com/ethernet/100quickref/ch14qr_2.html#HEADING1.
>Question 4: Isn't there some kernel of truth that 10BASE-T still allows longer cable runs, but it would be "out of spec"? (Something that was earlier stated on your website and in topic #1789 where Larry responds: "The maximum for 10 MHz 10BASE-T is 185 meters."
A 10BASE2 (thinwire coax) segment has a maximum length of 185 Meters. As I understand it, 100BASE-TX is limited to 100 Meters because of timing factors (the time required for a frame to propagate down the cable, latency, and a Ethernet a collision signal to return) whereas 10 BASE-T is limited (the timing limitation may be 185 Meters, or maybe it is the 300 Meters I originally stated in error—I’ll let someone else work the math on it, if does not becomes a real-world need.) by the electrical limitations of the twisted-pair cable (probably the capacitance between the wires) and nominally to 100 Meters. I have read that it can be extended, perhaps, up to 150 meters, but I wouldn’t bet a network installation on it. I will say that what I have read on the subject is probably old and may predate CAT 5 and 5E cable.
You might find some useful info in http://duxcw.com/dcforum/DCForumID2/1748.html. Larry