Network devices are used to connect computers or other electronic devices together. Network media and connectors are not enough to build a computer network. With the help of media and connectors, the oil is needed to make that network work efficiently. These devices include network interface card hubs or concentrators, repeaters, bridges, switches, routers, etc. For better network design and network administration, it is necessary to know the working of these devices and the rules for using them.

Network interface card

A computer needs a special interface to connect the network media to the corner. A network interface card or LAN card serves as this interface. This network adapter can provide connectivity to any media. There are different network adapters for different media and those computers can be connected to the network with suitable connectors. Not only a server or workstation that has a network interface card, a printer or other device can also have a network interface card. The network interface card uses special software called the driver to interoperate with the operating system of the computer. If it does not have a suitable driver, it cannot connect to the operating system and perform network functions.

Network interface card
Figure: Network Interface Card

If a network device wants to connect to another device, that device wants to get the MAC address of that device. This MAC address is used to know Address Resolution Protocol or ARP. ARP stores the MAC address of each device it knows on the ARP table. When the device is running near the ARP device, he informs the device from his ARP table. This allows the device to interact with other devices. This address table may be updated after a certain time.

The MAC address of the computer on the corner is kept in that table for a certain period of time. During that time, if the query does not come in the corner to know the MAC address of that computer, then it is deleted. After deleting the entry, if the query for that MAC address arrives, the ARP will retrieve it. The task of the ARP or address resolution protocol is to inform the MAC address of the physical device.


Figure: Hub

Except for bus topology, all topologies have to have a central system where cables from different workstations can be connected. If you are connecting the ends of that cable, the signals from one cable will flow to all the other and the network will not work. To prevent this from happening, the cables from different stations are connected to a central device. This device is called a hub or concentrator.

The hub works on the physical layer of the OSI reference model. Whatever the signal is, the hub will send it to different segments of that network. It works with electric signals. There is no hub headache with the network address or the MAC address of the network adapter.

The hub is in the view of a box and has a cable to give various cable connections. These jets usually use RJ-45 connectors. This twist can be connected through a twisted pair cable RJ-45 male connector. This twisted pair cable can then connect to the server or workstation at the corner. Each network that uses the UTP cable must use the hub. We can also think of a hub as a repeater with multiple ports. Because it receives an electrical signal from a cable, amplifies it and sends it to all other workstations. This is done in the physical layer of the OSI model.


We know that the signal continues to be weak due to the attenuation during signal transmission in different media. After passing a certain distance, its existence disappears. Existence signal before getting the lap to amplify or can make more strong, it can go far. For example, a bus on a thin coaxial cable on a 10Base2 network can have a length of up to 185 meters. If you use a bus longer than your network, the signal will not transmit. A repeater is used to amplify such signals. If you amplify the signal using a repeater before crossing a distance of 185 meters, it will be able to exceed 185 meters in the array. It works on the physical layer of the OSI reference model.

Figure: Repeater

Repeater two types: Amplifier and signal regenerating. The amplifier completely amplifies the signal. Amplifier repeater will also amplify this signal if there is no noise or nonorganic signal. He gave fertilizers in paddy fields, paddy trees grew, weeds and plants grew in parallel. This is the case with the amplifier repeater. If you want to exclude weeds only to grow crops, you can use a signal regenerating repeater in such a case. It reconstructs the signal after it has been received and eliminates the noisy or unpredictable signal from there. This results in improved network performance.


A bridge is a device by which two network segments can be connected. This is according to the Hub, but the procedures are different. This device works on the Data-Link layer of the OSI reference model. It works on the Data-Link layer so it can work with the OSI address of the network adapter. Based on the OSI address, it can decide which segment of the network to send the data packet to.


The bridge has four main functions:

  1. It creates bridging tables for calculating different devices in each segment. It contains the MAC addresses of different devices in both segments.
  2. By looking at the MAC address of a data packet, it can decide whether this packet needs to be sent to another part. If that MAC addressed heist is in the same segment, the bridge will not allow that packet to cross that segment. This filtering does not create unnecessary network traffic.
  3. If the MAC address of a data packet is checked and it is in the other part then the bridge sends it to that part.
  4. This splits a network into several collision domains, reducing the number of calls to the network.

Bridge uses the Spanning Tree Protocol (STP) to select this path and send it to different segments. The spanning tree protocol does two things. First, it identifies the main bridge or route that all bridging decisions will take; second, it will resist the bridging loop.

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