IP addresses: IPv4 and IPv6

By the end of this lesson

By the end you can describe the format of IPv4 and IPv6 addresses, shorten an IPv6 address, and explain how IP addresses are used to deliver packets.

Every parcel needs an address

Data crosses the internet in packets. A router holding a packet has one question: where is this going? The answer is written on the packet: an IP address.

Definition

IP address

A logical address given to a device on a network that identifies it, so that data packets can be routed to it. (Unlike a MAC address, it isn't fixed to the hardware and can change.)

How IP addresses deliver data

The data is split into packets.
Each packet's header holds the source IP address (the sender) and the destination IP address (the receiver).
Every router on the way reads the destination IP address to decide the next hop.
The receiver uses the source IP address to send its reply back.

IPv6 addresses are four times longer than IPv4 ones, which gives a mind-boggling number of them.

The two formats

	IPv4	IPv6
Length	32 bits	128 bits
Written as	4 denary numbers (0–255), one per 8 bits, separated by dots	8 groups of 4 hexadecimal digits, one per 16 bits, separated by colons
Example	`192.168.10.77`	`2001:0db8:0000:0000:0000:ff00:0042:8329`
Number of addresses	$2^{32}$ ≈ 4.3 billion	$2^{128}$ ≈ $3.4 \times 10^{38}$

Why IPv6? With phones, laptops, smart TVs and smart fridges, 4.3 billion IPv4 addresses ran out. IPv6 provides enough for every device imaginable.

Worked example: Is this a valid IPv4 address?

Which of these are valid IPv4 addresses? (a) 172.16.254.3 (b) 10.0.256.1 (c) 192.168.1

Have a go first?

Quick check

Multiple choiceQuestion 1 · Recall

CalculateQuestion 2 · Recall

Fill in the blanksQuestion 3 · Apply

Answer the 3 questions above to continue.