Address Resolution Protocol (ARP)

ARP: Resolving IP Addresses to MAC Addresses

Purpose of ARP

ARP (Address Resolution Protocol) serves two primary functions:

• IP-to-MAC Resolution: When a device needs to send a packet to another on the same network, it uses ARP to determine the destination device's MAC address.
• IP-to-MAC Cache: ARP maintains a cache of resolved IP-to-MAC mappings to reduce the frequency of ARP requests and improve network performance.

How ARP Works

1. ARP Request: A device broadcasts an ARP request to the network, inquiring about the MAC address associated with a specific IP address.
2. ARP Reply: The device owning the target IP address responds with an ARP reply, providing its MAC address.
3. Cache Update: The requesting device caches the IP-to-MAC mapping for future use.

ARP Poisoning

A malicious attack known as ARP poisoning involves sending forged ARP replies to redirect network traffic to an attacker-controlled device. This can disrupt network communication and compromise security.

VRRP: Virtual Router Redundancy

VRRP (Virtual Router Redundancy Protocol) ensures high availability for virtual routers. Multiple devices can share a virtual IP address, and VRRP automatically takes over if the active device fails.

ARP in Load Balancing

ARP can be used to distribute traffic among multiple servers in a network. By assigning different MAC addresses to servers, load balancing can be achieved, ensuring efficient resource utilization.

Summary

ARP is a fundamental protocol for network communication, enabling devices to resolve IP addresses to MAC addresses. While ARP poisoning poses a security threat, its proper implementation is essential for well-functioning networks.