The 5-4-3 Rule in Thinnet
A thinnet network can combine as many as five cable segments connected by four repeaters; but only three segments can have stations attached. Thus, two segments are untapped and are often referred to as "inter-repeater links". This is known as the 5-4-3 rule.
Because the normal Ethernet limits can be too restrictive for a large business, repeaters can be used to join Ethernet segments and extend the network to a total length of 925 metres (3035 feet).
Note: Sometimes the 5-4-3 rule is referred to as the 5-4-3-2-1 rule, with the 2 being two unpopulated segments and the 1 referring to one collision domain.
Next: 10Base5 Standard