MAC Addresses & IP Addresses (Cambridge International IGCSE Computer Science)

• Devices on a network send and receive data, a device needs an address to ensure it sends data to the correct place

• There are two types of network address systems:

  • MAC Address
  • IP Address

MAC Addresses

Spec point — 3.4.2 · "2 Understand what is meant by and the purpose of a media access control (MAC) address, including its structure"

MAC Addresses

What is a MAC address?

• A MAC (Media Access Control) address is a unique identifier given to devices which communicate over a local area network (LAN)
• A network interface card is given a MAC address at the point of manufacture
• MAC addresses are static, meaning they can never change
• MAC addresses make it possible for switches to efficiently forward data to the intended recipient
• Any device that contains a Network Interface Card (NIC) has a MAC address assigned during manufacturing
• A device connecting to a local network already has a MAC address, if it moves to a different network then the MAC address will stay the same

• A MAC address is represented as 12 hexadecimal digits (48 bits), usually grouped in pairs
• The first three pairs are the manufacturer ID number (OUI) and the last three pairs are the serial number of the network interface card (NIC)
• There are enough unique MAC addresses for roughly 281 trillion devices

IP Addresses

Spec point — "3 (a) Understand what is meant by and the purpose of an internet protocol (IP) address (b) Understand that there are different types of IP address"

IP Addresses

What is an IP address?

• An IP (Internet Protocol) address is a unique identifier given to devices which communicate over the Internet (WAN)
• IP addresses can be static, meaning they stay the same or dynamic, meaning they can change
• Static IP addresses are commonly used for servers and websites so they can always be found at the same address
• Dynamic IP addresses are assigned automatically by a DHCP server (Dynamic Host Configuration Protocol)
• IP addresses make it possible to deliver data to the right device
• A device connecting to a network will be given an IP address, if it moves to a different network then the IP address will change

IPv4

• Internet Protocol version 4 is represented as 4 blocks of denary numbers between 0 and 255, separated by full stops
• Each block is one byte (8 bits), each address is 4 bytes (32 bits)

• IPv4 provides over 4 billion unique addresses(2³²), however, with over 7 billion people and countless devices per person, a solution was needed

IPv6

• Internet Protocol version 6 is represented as 8 blocks of 4 hexadecimal digits, separated by colons
• Each block is 2 bytes (16 bits), each address is 16 bytes (128 bits)

• IPv6 could provide over one billion unique addresses for every person on the planet (2¹²⁸)

Worked Example Computers in a network can be identified using both IP addresses and MAC addresses.

Describe two differences between IP addresses and MAC addresses [2]

Answer

• IP address is dynamic/can change // MAC address is static/cannot change
• IP address is used to communicate on a WAN/Internet // MAC address is used to communicate on a LAN