How many 10 Mbps repeating hubs can I cascade and how long can the cables be?
With shared Ethernet (half-duplex) you need to follow the rules in IEEE 802.3. The easiest method is the 5-4-3 rule which means a maximum of five segments, four repeaters (hubs) and only three mixing segments. Mixing segments are coaxial segments and since they are not popular let’s ignore them. Therefore, if you have all twisted-pair segments and four hubs, the maximum end-to-end length (diameter) of your network is 500 meters. Let’s say you want to have twisted-pair at the ends and fiber interconnecting the hubs, there are restrictions on the fiber length. Even though each fiber segment (10BASE-FL) can be up to 2 km, the total amount of fiber cannot exceed that amount. The standard specifically states that with a four segment, three-repeater network, the two inter-hub fiber segments cannot exceed 1 km each. Actually a better way of saying it is that the sum of the two segments cannot exceed 2 km. With this restriction, the maximum network diameter would be 2200 meters. The 5-4-3 rule
