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When we talk about network operation, networks do not normally operate in isolation. In a network LAN, MAN or WAN are connected to one another or to the internet. To connect LAN subdivisions, we use Network devices.

There are five types of network devices are used, such as
1.   Repeater.
2.   Hub.
3.   Bridge
4.   Router.
5.   Gateway.

These devices can operate in different layers of Internet model.

Let’s start with these devices,

1. Repeater: Repeater is a device that operates only in physical layer. It receives a signal, and before it becomes too weak or damaged, the repeater regenerates the signal’s original bit pattern. Then the repeater resends the refreshed signal.

Basically, a repeater connects several segments of LAN and extends the physical length of the LAN by connecting it.

Note: A repeater just forwards every frame, but it has no filtering capability. So it’s more of a regenerator than amplifier.

2. Hub: There are two types of hub.
                a) Passive hub.
                b) Active hub.

A Passive hub is nothing but a connector between wires. It connects different branches of wires.
An Active hub is a multiport repeater. It’s normally used to create connections between computers, just like we used in star topology of physical layer in OSI model.

3. Bridges: A bridge is a networking device that operates both in Physical and Data link layer. That’s why it’s also known as Two-layer switch.

In physical layer, a bridge just regenerates the signal it receives it.

But in data link layer, a bridge has filtering capability. It can check the MAC addresses (source and destination address) in the frame and decide whether the frame should be forwarded or be dropped.

Note: A bridge checks the MAC addresses in a frame, it does not change it.

4. Router: A router is a three-layer switch which operates in Network layer as well as Physical and Data link layer. A router mainly used to route packets based on IP addresses; from source host to destination host (Host-to-host addressing).

Now it’s easy to understand why a router is used in network layer,
because network layer is responsible for Host-to-host delivery of packets and a router does the routing of those packets based on the logical addresses of source host and destination host.

5. Gateway: It’s a networking device that operates in all five layer in TCP/IP model and seven layers in OSI model. A gateway is generally a computer that takes an application message, reads it and interprets it. This means it can be used as a connecting device between two inter-networks that use different models..
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Now, let’s summarize all the networking devices in a nutshell

network router, network gateway
Network devices
  • The repeater and hub both operates only in physical layer.
  • However, the bridge operates in both data link layer and physical, which is why it’s called two-layer switch.
  • The router operates in network layer as well as data link layer and physical layer, and that’s why it’s called three-layer switch.
  • Finally gateway operates in all seven layers of OSI model or all five layers in Internet model.

Study Sessions

Q1. How is the network repeater is different from an amplifier?

Q2. What are the differences between hub, bridge and a router?

Q3. How hub is related to the repeater?

Q4. What filtering traffic by network bridge? Explain why filtering is so important?


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