To ensure a smooth and efficient network system with the ability to connect to other networks, specialized networking devices are required. These devices are diverse and varied in type but are all based on fundamental devices such as Repeaters, Hubs, Bridges, Switches, Routers, and Gateways.
This article aims to provide readers with a basic understanding of the aforementioned networking devices:
Repeater
In a Local Area Network (LAN), the cable length limit is 100 meters (for CAT 5 UTP cables – the most commonly used type), as signals degrade over distance and cannot travel further. Therefore, to connect devices that are farther apart, the network requires devices to amplify and regenerate the signals, allowing them to transmit beyond this limit.
A Repeater is a device at Layer 1 (Physical Layer) of the OSI model. Its role is to amplify the physical signal at the input and provide power to the output signal so that it can reach the next stages in the network. Telegraphy, telephony, fiber optic communications, and other long-distance signal transmission needs all require Repeaters.
Hub
A Hub is often seen as a Repeater with multiple ports. 
A Hub can have between 4 to 24 ports or even more. In most cases, Hubs are used in 10BASE-T or 100BASE-T networks. When the network configuration is in a star topology, the Hub serves as the network’s center. With a Hub, when information enters from one port, it is sent to all other ports.
There are two types of Hubs: Active Hubs and Smart Hubs. An Active Hub is the more commonly used type, requiring power to operate, and is used to amplify incoming signals and transmit them to the remaining ports, ensuring adequate signal levels. A Smart Hub (Intelligent Hub) functions similarly to an Active Hub but includes an integrated chip that can automatically detect faults, which is very useful for troubleshooting and error detection in the network.
Bridge
A Bridge is a networking device that operates at Layer 2 of the OSI model (Data Link Layer). 
Bridges are used to connect two networks to form a single larger network. They are commonly used as a bridge between two Ethernet networks. A Bridge monitors packets across all networks. When it detects a packet from a computer in one network being sent to a computer in another network, the Bridge copies and sends that packet to the destination network.
Advantages of a Bridge include its transparent operation, allowing computers from different networks to communicate simply without being aware of the Bridge’s “interference.” A Bridge can handle multiple traffic types on networks like Novell and Banyan, as well as IP addresses simultaneously. Disadvantages of a Bridge include its limitation to connecting similar types of networks, and using a Bridge for high-speed networks can be challenging if they are not physically close to each other.
Switch
A Switch is sometimes described as a Bridge with multiple ports. While a 
Bridge has only 2 ports to connect 2 network segments, a Switch can connect multiple segments depending on the number of ports it has. Similar to a Bridge, a Switch “learns” information about the network through the packets it receives from devices on the network. It uses this information to build a Switch table, which provides information that helps packets reach their correct destination.
Nowadays, in data communications, a Switch typically has two main functions: forwarding data frames from source to destination and building Switch tables. Switches operate at much higher speeds than Repeaters and can offer additional features like the ability to create Virtual Local Area Networks (VLANs).
Router 
A Router is a Layer 3 device in the OSI model (Network Layer). It connects two or more IP networks. Computers on the network must be aware of the Router’s presence, but one of the rules of IP is that any computer connected to the network can communicate with the Router.
Advantages of a Router: Physically, a Router can connect different types of networks, from high-speed local Ethernet to slower long-distance telephone lines.
Disadvantages of a Router: Routers are slower than Bridges because they require more processing to determine how to route packets, especially when connecting networks that operate at different speeds. A fast network can send packets much quicker than a slow network, potentially causing congestion. Therefore, a Router may require computers to send packets at a slower pace. Another issue is that Routers are specialized according to protocol – meaning that the way a computer communicates with an IP router differs from how it communicates with a Novell or DECnet router. This issue is now addressed by a network that understands the pathways of all known network types. All commercial routers can handle multiple types of protocols, often at an additional cost per protocol.
Gateway
A Gateway allows the interconnection of two different protocols. For example, if your network uses the IP protocol and someone else’s network uses IPX, Novell, DECnet, SNA, or any other protocol, the Gateway will convert from one type of protocol to another.
Through the Gateway, computers on different networks using different protocols can easily “communicate” with each other. Gateways not only differentiate protocols but can also distinguish applications, such as how you transfer emails from one network to another or switch a remote session…
