Address Resolution Protocol ARP In Networking

Address Resolution Protocol ARP In Networking

This article is an introduction to the Address Resolution Protocol ARP In Networking. You will learn what it ARP, how ARP works, what is purpose of ARP.

Remember that each device in an Ethernet network has an IP address and an Ethernet MAC address. When a device sends an Ethernet frame, it contains these two addresses:

• Destination MAC Address : The MAC address of the Ethernet NIC, which is the address of the final destination or router.
• Source MAC address: the MAC address of the sender's Ethernet NIC.

DIFFERENCES BETWEEN MAC AND IP

The combination of MAC and IP facilitates end-to-end communication. While the Layer 2 (MAC) addresses are used to move the frame within the local network. Layer 3 (IP) addresses are used to move packets across remote networks.

Main differences:

• The MAC address does not change ("it is a person's ID"), while the IP address is similar to a person's address.
• The MAC address is known as " physical address"  because it is physically assigned to the host NIC. The IP address is known as the " logical address"  because it is logically assigned.
• In order for a PC to communicate, both the physical MAC address and the logical IP address are required

FUNCTIONS OF THE Address Resolution Protocol ARP in networking

The sending node needs a way to find the MAC address of the destination for a given Ethernet link and this is how ARP appears, which allows the origin to request the MAC address of the destination. The request is based on the Layer 3 address of the destination (known by the origin).

• To determine the destination MAC address, the device uses ARP. ARP provides two basic functions:
• Resolution of IPv4 addresses to MAC addresses
• Maintenance of an assignment table

The functions of the ARP are as follows:

• Resolution of IPv4 addresses to MAC addresses : The ARP table or ARP cache (which is stored in the device RAM), allows you to find the MAC address that is assigned to an IPv4 address.
• Maintenance of an assignment table:
• ARP uses the ARP Request and the ARP Response to perform its functions.

For each device, an ARP cache timer removes ARP entries that have not been used for a specified period.

PROBLEMS IN ARP

There are two types of problems regarding ARP:

• ARP broadcasts : ARP requests can saturate the local segment.
• ARP impersonation : (ARP poisoning) This is a technique used by an attacker to respond to an ARP request from an IPv4 address that belongs to another device, such as the default gateway. The attacker sends an ARP response with its own MAC address. The ARP response recipient adds the wrong MAC address to the ARP table and sends these packets to the attacker.