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OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography


Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network Open Loop and Closed Loop Congestion Control Types of Cluster Computing WAP-Wireless Access Point What are the elements of the Transport Protocol Difference between Gateway and Switch Flow Control in Data Link Layer Body Area Network Flooding in Computer Network

Working of ARP

The majority of computer programmes and applications send and receive messages using logical addresses (IP addresses), but the actual communication takes place over physical addresses (MAC addresses), which is found in layer 2 of the OSI model.

Our objective is to find the destination MAC address so that we can communicate with other devices. Because ARP transforms IP addresses into Mac addresses or physical addresses, which is helpful in this situation.

A new computer that joins a LAN is specified by a special IP address that is used for identification and communication. The ARP program will be asked to locate a MAC address that matches the IP address when a packet is incoming from a host computer on a particular LAN reaches the gateway.

A host first determines whether the IP to Mac address translation is present or not in the ARP cache when it requests a MAC address to send a packet to another host in the LAN. If it exists, a new ARP request is not required and if the translation is not exist a request for network addresses is sent before an ARP operation.

ARP sends a request packet to every device on the LAN if any LAN machine use the particular IP address.

The ARP Request message will be broadcast throughout the local network by the source computer. Every device connected to the LAN network receives the broadcast message.

Instead of being broadcast, the ARP Reply message is unicast. This is so because the device from which the ARP Reply message is being sent is aware of the MAC address of the device from which the message is being received.

The destination's MAC address will be updated by the source in the ARP cache. The sender can now communicate with the receiver directly.

Network devices transfer the packet to the network layer after removing the frame's protocol data unit (PDU) called the data link layer's header (layer 3 of OSI).

If the network IDs of the source and destination IPs match, the destination's MAC address is returned to the source, otherwise, the packet reaches the network gateway, which broadcasts it to the connected devices and verifies their network IDs.

The above-said procedure continues up until the second last network device in the path arrives at the destination, at which point it is validated and ARP replies with the destination MAC address.

The request message or field in ARP contains many important terms like:

1. Hardware Type: It describes the type of hardware that is used to send the ARP message.The most popular kind of hardware is Ethernet.

2. Protocol Type: It describes the protocol type (hex, decimal, etc.) Each protocol is specified as a number. And in this case, the IPv4 protocol is a hex type protocol which is commonly used.

3. Protocol Size: It describes the length or size of the protocol. Here the size of the IPv4 address is 4 bytes.

4. Opcode: It describes the ARP message's code or nature. For Example, 1 represents an ARP request, and 2 represents an ARP response.

5. Source IP Address: It contains source IP address like

6. Destination(Target) IP Address: It contains a destination IP address like

7. Source MAC Address: It contains Source Mac Address like 00:1a:6b:6c:0c:cc

Advantages Of ARP

  • The main benefit of a proxy ARP is that it can communicate with every machine on the network with the help of one router.
  • If we are aware of the device's IP address, we can quickly determine the MAC address of that device by using ARP.
  • It is not necessary to set the end nodes addresses for the MAC address. If necessary, we can locate it.

Disadvantages of ARP

  • The main drawback is that hosts on a network build up more information in their ARP tables because they believe that all other machines are reachable via an ARP request.
  • It boosts ARP traffic in your segment.
  • Larger ARP tables are required by hosts to manage IP-to-MAC address mappings.
  • Security threats are possible.
  • Networks without ARP-based address resolution are not supported by it.
  • It does not apply to every network topology.

Why is ARP important?

ARP is required because it converts the host software address into a hardware address (MAC address). A host is unable to determine the hardware address of another host without the use of ARP. The local area network (LAN) maintains a table or directory that converts IP addresses to MAC addresses for various devices, including routers and endpoints.

Users or even IT administrators are not responsible for maintaining this table or directory. Instead, the ARP protocol generates entries when required.

ARP Spoofing

ARP spoofing is also known as ARP poison routing and ARP cache poisoning. In this malicious attack, a hacker sends phony ARP messages to a target LAN in an effort to associate their MAC address with the IP address of a reliable server or device on the network.

Data from the victim's computer can be sent through the link to the attacker's machine instead of the original destination. Attacks using ARP spoofing can be risky because sensitive data may be transferred between computers without the victim's knowledge.


Our objective is to find the destination MAC address so that we can communicate with other devices. Because ARP transforms IP addresses into Mac addresses or physical addresses, which is helpful in this situation.