Understanding ARP (Part 1) – MAC Address

ARP stands for Address Resolution Protocol. ARP is used to mapping computer IP addresses to computer hardware addresses. In the next three days, let’s see how ARP works.

Medium Access Control (MAC) Address

To understand what is Address Resolution Protocol (ARP), let’s has some basic concept of Medium Access Control (MAC) Address.

Medium Access Control Address is the hardware address which store in the PROM of each Network Interface Card (NIC). Each Network Interface Card is assigned an Ethernet source address by the manufacturer. The address (MAC Addresses) of each Network Card is globally unique. In other words, no two Network Interface Cards will ever have the same source address. That’s why each computer on the Internet has a unique address.

An Important Concept

All computers in the network are using their MAC Addresses to communicate with each others. Therefore when one computer want to communicate with other computers in the network, their MAC Addresses must be known. The situation is same as the diagram below:

MAC Address

How About IP Address?

Wait…. Aren’t the computers in the network using their IP Addresses to communicate with each others? I sometimes use their IP addresses?  But I never use or never know their MAC Addresses!

Let’s talk more about MAC Addresses in my next blog.

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