Running out of addresses
IPv4 has about four billion addresses. That sounded like plenty in the 1980s. Now every phone, watch, car and doorbell wants one.
The world ran short. The answer is IPv6, with so many addresses that running out is not a worry.
Key words
| Word | What it means |
|---|---|
| IPv6 | the newer way to give devices addresses, with 128 bits |
| Hexadecimal | a number system with sixteen digits, 0 to 9 and then A to F |
| Group | four hex digits in an IPv6 address, between colons |
| Unicast | an address for one device, and a message goes to that one |
| Global unicast | a public address that works on the internet |
| Link-local | an address that works only on the local link, never further |
| Unique local | a private address, like a private IPv4 address |
| Multicast | an address for a group of devices, and a message goes to all of them |
| Anycast | one address given to several devices, and the nearest one answers |
| Loopback | the address a device uses to talk to itself |
| Network | computers and devices joined together so they can share data |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can read and shorten an IPv6 address, and name the main types of address and what each is for.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
What an IPv6 address looks like
An IPv6 address is 128 bits. We write it in hex, as eight groups of four digits, with colons between: 2001:0db8:0000:0000:0000:0000:0000:0001.
That is long, so there are two shortening rules.
Two rules to shorten an address
| Rule | Before | After |
|---|---|---|
| 1. Drop leading zeros in each group | 2001:0db8:0000:0000 | 2001:db8:0:0 |
| 2. Replace one run of all-zero groups with two colons | 2001:db8:0:0:0:0:0:1 | 2001:db8::1 |
| Both rules together | 2001:0db8:0000:0000:0000:0000:0000:0001 | 2001:db8::1 |
| Both rules on a link address | fe80:0000:0000:0000:0202:b3ff:fe1e:8329 | fe80::202:b3ff:fe1e:8329 |
The cells students fill in are left blank in this preview.
Use two colons only once
Important
Two colons can stand for a run of zero groups, but only once in an address. If you used it twice, nobody could tell how many zero groups each one hides.
Check
Have a go
Check
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.