The 5-4-3 Rule for Repeaters

A repeater can connect Ethernet segments operating at the same transmission speed together to create a larger LAN. The repeater regenerates the signal as it passes from one segment to another. The 5-4-3 rule is important when considering using repeaters (or hubs) to build a larger Ethernet LAN:

5 - No path between any two end systems (NICs or other equipment) may traverse more than FIVE Ethernet segments.

4 - No path between any two NICs may traverse more than FOUR Ethernet hubs or repeaters.

3 - No more than THREE of the five segments on the longest path may be active segments (i.e. segments with more than two nodes and/or repeater ports). The remaining two segments must be passive point- to-point links.

The 5-4-3 rule applies to the furthest connection between NICs connected across the LAN. In practice, by choosing a suitable design, a large number of hubs and repeaters may be combined to produce a required network topology.

Connecting more segments or segments with different speed of operation requires the use of an Ethernet Bridge.

See also:


Ethernet Hubs

Ethernet Bridges

A page shows examples of various types of networking equipment, including Bridges and Switches for Ethernet.

Manged Switches

Gorry Fairhurst - Date: 1/1/2020