Ethernet can run up to 500m on a half-duplex link (thick coax). There is a limit for the total network diameter to ensure that collisions are still detected, but there's no way you're going to exceed it with a single twisted pair link.
I should have clarified that the 100 meter limit is for 100 megabit and gigabit Ethernet. For 10 megabit Ethernet the limit is 500 meters
per backbone segment, but you can go something like 2500m (IIRC) end-to-end, through repeaters. It was designed so that you could have a 1500m fiber segment bridging between two "ethers."
Actually, the 100 meter limit is for all twisted pair based Ethernet, 10baseT, 100baseT, and 1000baseT.
(the following is mostly of historical interest, since no one actually builds shared networks of this size any more.)
For 10base5 (Thicknet) the limit is 500 meters per segment. For 10base2 (Thinnet) the limit is 185 meters per segment.
The 5-4-3 rule applies. Between any two stations in a shared Ethernet network, you may have up to 5 segments, with 4 repeaters (hubs are considered multi-port repeaters), but only 3 segments may be populated with stations. If you are using 10base5, this means that there can be a maximum of 3000 meters between end stations before a router or bridge is required. 3000 meters is based on 5x
500m 10base5 coax segments, and 10x
50m AUI transceiver cables (ie:
[HOST]-
50m-(X)-
500m-(X)-
50m-
[REPEATER]-
50m-(X)-
500m-(X)-
50m-
[REPEATER]-
50m-(X)-
500m-(X)-
50m-
[REPEATER]-
50m-(X)-
500m-(X)-
50m-
[REPEATER]-
50m-(X)-
500m-(X)-
50m-
[HOST]If you need to extend the network beyond these limits, you need to segment the collision domain with a router or a bridge (a switch is essentially a multi-port bridge).
A DEC remote repeater uses up to 1000 meters of fiber optic cabling to connect two network segments. FOIRL (Fiber Optic Inter Repeater Link) also has a 1000 meter limitation. 10base-FL, which replaces FOIRL, has a 2000 meter limit.
I believe that you are allowed to replace one segment with a fiber optic remote repeater, based on the old DEC configuration guidelines.
