Active hubs, passive hubs, and repeaters are layer-1 devices. They connect two or more devices to the computer network. They are the foundation of the Ethernet network.
Repeaters
Repeaters circumvent the maximum length limitation of twisted-pair cables. A repeater consists of two RJ45 ports connected internally by an amplifier. When it receives electrical signals on one port, it amplifies and forwards them through the other port. Amplified signals can travel the maximum supported length again.
Let us take an example.
Suppose you want to connect two end devices located at a distance of 150 meters through a twisted-pair cable. A twisted-pair cable supports a maximum length of 100 meters.
In this case, you can use a repeater to amplify the signals in the cable.
Hubs
Technically, a hub is a multiport repeater. A hub does the same thing a repeater does. But a hub does it on a large scale. The main difference between a hub and a repeater is a repeater has only two ports while a hub has many ports. For example, a hub may have eight or sixteen ports.
Hubs generally have light-emitting diode (LED) indicator lights to indicate the status of each port, link status, collisions, and other information.
There are two types of hubs: active hubs and passive hubs. The main difference between both types is an active hub amplifies signals before forwarding them while a passive hub forwards them as they are. So far functionality is a concern, both work similarly. When they receive an electrical signal on any port, they forward it from all other ports.
Let us understand it through an example.
An eight-port hub receives electric signals on port 1. It forwards them from ports 2 through 8. If it receives electric signals on port 4, it forwards them from ports 1 through 3 and ports 5 through 8.
Hubs typically have one or more uplink ports that are used to connect them with another hub. Uplink ports allow us to expand the network.
You can connect an uplink port on one hub to a regular port on another hub using a straight-through cable. Alternatively, you can connect two hubs using the uplink ports by using a crossover cable.
For example, on an eight-port hub, you can connect seven computers and another eight-port hub on the uplink port. You can connect seven computers to another hub. In this way, two eight-port hubs can connect 14 computers to each other.
Hubs are no longer used in modern networks. They are replaced with switches. Switches forward data more intelligently.
