ARP

Definition

ARP, or Address Resolution Protocol, is a network protocol used to map an Internet Protocol (IP) address to a physical machine address that is recognized in the local network. It plays a crucial role in enabling devices to communicate over Ethernet and other types of networks by providing a mechanism for discovering the hardware address associated with an IP address, thus facilitating data transmission and connectivity in various network architectures.

5 Must Know Facts For Your Next Test

1. ARP operates at the link layer of the OSI model and is essential for resolving IP addresses into MAC addresses for local area networks.
2. When a device wants to communicate with another device on the same local network, it broadcasts an ARP request to find out the MAC address associated with the target IP address.
3. If the target device receives the ARP request and recognizes its own IP address, it responds with an ARP reply, providing its MAC address back to the requester.
4. ARP can also be susceptible to certain security vulnerabilities, such as ARP spoofing, where an attacker sends false ARP messages to associate their MAC address with the IP address of another device.
5. In IPv6 networks, ARP has been replaced by Neighbor Discovery Protocol (NDP), which serves similar purposes but operates more efficiently and securely.

Review Questions

• How does ARP facilitate communication between devices in a local network?
  • ARP facilitates communication by converting an IP address into a MAC address, which is required for devices on the same local network to send data to each other. When one device wants to communicate with another, it sends an ARP request that includes the target IP address. The device with that IP address responds with its MAC address, allowing data packets to be delivered correctly on the local network.
• Discuss how ARP requests and replies work in a typical local area network environment.
  • In a typical local area network environment, when a device needs to send data to another device but only knows its IP address, it broadcasts an ARP request asking for the MAC address associated with that IP. The device with that IP then replies directly with its MAC address. This exchange allows the sending device to create frames that include the correct MAC destination, ensuring successful data transmission over Ethernet.
• Evaluate the implications of ARP spoofing on network security and propose potential countermeasures.
  • ARP spoofing poses significant risks to network security as it can lead to man-in-the-middle attacks, where attackers intercept or modify communications between devices. This vulnerability arises because ARP does not authenticate responses. To mitigate this risk, network administrators can implement static ARP entries for critical devices, use security protocols such as Dynamic ARP Inspection (DAI) on switches, or adopt more secure protocols like IPv6's Neighbor Discovery Protocol (NDP), which incorporates security features to prevent such attacks.

Related terms

IP Address: A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.

Ethernet:

A widely used networking technology that connects devices in a local area network (LAN) using cables and switches.

MAC Address: A hardware identification number that uniquely identifies each device on a network, used in the data link layer of the OSI model.