OCR J277 Topic 1.3.2

IP and MAC Addressing

How devices find each other and route data across networks.

Learning Checklist

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1

IP Addresses

An IP (Internet Protocol) address is a logical address used to route data across wide area networks (WANs), like the internet. Think of it like your home's postal address; it tells the internet exactly where to deliver your data.

Exam Trap: Spot the Fake IPv4!

Examiners love to ask you to identify invalid IPv4 addresses. Remember: An IPv4 address is made of 4 numbers, and no single number can be higher than 255.

For example, 192.168.1.1 is valid.
258.0.0.3 is invalid because 258 is too high!

IPv4 Format

The older, most common standard. We are actually running out of IPv4 addresses because there are too many devices in the world!

192.168.0.24
  • Made of 4 groups of numbers.
  • Uses standard denary (base-10) numbers.
  • Numbers range from 0 to 255.
  • Separated by full stops.
  • 32 bits long in total.

IPv6 Format

The newer standard created to solve the shortage. It provides enough unique addresses for every grain of sand on Earth!

2001:0db8:85a3:0000:0000:8a2e:0370:7334
  • Made of 8 groups of numbers/letters.
  • Uses hexadecimal (base-16) numbers.
  • Separated by colons.
  • 128 bits long in total.
2

MAC Addresses

A MAC (Media Access Control) address is a physical hardware address. It is a unique serial number permanently assigned to a device's Network Interface Card (NIC) by the manufacturer in the factory.

The Anatomy of a MAC Address

00:1A:2B : 3C:4D:5E

First Half

Contains the Manufacturer ID. This tells the network exactly who built the device (e.g., Apple, Dell, or Samsung).

Second Half

Contains the Serial Number. This uniquely identifies your specific device.

  • Made of 6 pairs of numbers/letters.
  • Uses hexadecimal numbers.
  • Separated by colons (:) or hyphens (-).
  • Only used to route data within a Local Area Network (LAN).
3

IP vs. MAC: Active Recall

The exam will often ask you to describe the differences between IP and MAC addresses. Test your knowledge by clicking the panels to reveal the answers!

Can the address be changed?
Reveal Answer

IP Address:

Yes. It is allocated by software. If you move your laptop to a new coffee shop, it gets a brand new IP address.

MAC Address:

No. It is permanently burnt into the hardware (NIC) in the factory and cannot be changed.

Where is it used to route data?
Reveal Answer

IP Address:

Used to route data across a WAN (Wide Area Network), like the internet.

MAC Address:

Only used to route data within a LAN (Local Area Network), usually by the Switch.

How is it written?
Reveal Answer

IP Address (IPv4):

Written using standard Denary numbers (0-255), separated by full stops.

MAC Address:

Written using Hexadecimal numbers, separated by colons or hyphens.

What you DON'T need to know: The OCR specification explicitly states you do not need to memorise the difference between static and dynamic, or public and private IP addresses for this exam! Keep your revision focused.

Key Vocabulary

Denary: The base-10 number system humans use every day (0-9).
Hexadecimal: A base-16 number system often used in computing to make long binary strings easier to read (0-9 and A-F).
NIC (Network Interface Card): Internal hardware that allows a device to connect to a network.

Lesson Summary & Review

Make sure all items are checked off before moving on to Lesson 3: The Rules of the Web (Protocols).