← IGCSE Computer Science Paper 1

IPv6 address format

A 128-bit address written as eight groups of four hex digits separated by colons, e.g. 2001:0DB8:0000:0000:0000:FF00:0042:8329

Part of: IGCSE Computer Science 0478 — 3.4 Network Hardware — Module 17, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 19, WA Computer Science ATAR Year 11 — Network Communications — Module 41

Understanding IPv6 address format in IGCSE Computer Science Paper 1

What it does: The colons between the eight groups are the IPv6 separator. IPv4 uses full stops instead. Every group is four hex digits long, with leading zeros kept in the full form, and only uses the digits 0-9 and letters A-F. An IPv6 address is 128 bits long. 32 bits is the length of an IPv4 address. IPv6 is written in hexadecimal, so the letters A to F are allowed as well as 0 to 9.

Common mistakes: Each hex digit stands for 4 bits, so the total is 8 groups x 4 digits x 4 bits = 128 bits. The line should multiply by 4, not 8. Hexadecimal digits only go from 0 to 9 and A to F. G is not a valid hex digit, so the group should be '00FF'.

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Learning
Duo
How many bits are in an IPv6 address?
128 bits32 bits
Matches
2001:0DB8:0000:0000:FF00:0042:8329
↓
Only seven groups are shown. A full IPv6 address needs eight groups.
Applying
Meanings
Term
IPv6 address
Meaning
A 128-bit address written as eight groups of four hex digits separated by colons, e.g. 2001:0DB8:0000:0000:0000:FF00:0042:8329
Practice
2001:0DB8:0000:0000:0000:FF00:0042:8329
Testing
Gaps
An IPv6 address is bits long.
Check Answer
Spots
2digits = 4
3bits = groups * digits * 8

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Quick Questions

1. How many bits are in an IPv6 address?
A. 32 bits
B. 128 bits ✓
An IPv6 address is 128 bits long. 32 bits is the length of an IPv4 address.
2. How many groups does a full IPv6 address have?
A. Eight groups ✓
B. Four groups
A full IPv6 address has eight groups. Four groups is the IPv4 layout (four numbers).
3. Which character separates the groups in an IPv6 address?
A. A colon : ✓
B. A full stop .
IPv6 groups are separated by colons. Full stops separate the numbers in an IPv4 address.
4. How many hexadecimal digits are in each group of a full IPv6 address?
A. Two hex digits
B. Four hex digits ✓
Each group has four hex digits. Four digits x 4 bits = 16 bits per group, and 8 groups x 16 bits = 128 bits.
5. Which one is written in the correct IPv6 format?
A. 2001:0DB8:0000:0000:0000:FF00:0042:8329 ✓
B. 2001.0DB8.0000.0000.0000.FF00.0042.8329
IPv6 uses colons between the groups. The version with full stops uses the wrong separator.

Match the Pairs

2001:0DB8:0000:0000:0000:FF00:0042:8329 → A full IPv6 address: eight groups of four hex digits separated by colons
2001:0DB8:0000:0000:0000:FF00:0042:8329 = 128 bits → Eight groups x 16 bits per group (4 hex digits x 4 bits) gives 128 bits in total
IPv6 groups are separated by colons, not full stops like IPv4 → FE80:0000:0000:0000:0202:B3FF:FE1E:8329
Each IPv6 group has exactly four hex digits (0-9 and A-F) → 2001:0DB8:ABCD:0012:0000:0000:00FF:1A2B
2001:0DB8:0000:0000:FF00:0042:8329 → Only seven groups are shown. A full IPv6 address needs eight groups.
2001.0DB8.0000.0000.0000.FF00.0042.8329 → Full stops are used as separators. IPv6 groups must be separated by colons.

Key Term

IPv6 address
A 128-bit address written as eight groups of four hex digits separated by colons, e.g. 2001:0DB8:0000:0000:0000:FF00:0042:8329

Fill in the Blanks

1. An IPv6 address is 128 bits long.
Hint: Type the total number of bits in an IPv6 address.
2. An IPv6 address has 8 groups of hex digits.
Hint: Type how many groups make up an IPv6 address.
3. Each IPv6 group has 4 hex digits.
Hint: Type how many hex digits are in each group.
4. IPv6 groups are separated by a colon.
Hint: Type the name of the punctuation character that separates the groups.
5. 8 groups x 4 digits x 4 bits = 128 bits
Hint: Type the number of bits that one hex digit represents.

Spot the Error

Question 1
A groups = 8
B digits = 4
C bits = groups * digits * 8
Line C — Each hex digit stands for 4 bits, so the total is 8 groups x 4 digits x 4 bits = 128 bits. The line should multiply by 4, not 8.
Question 2
A g1 = '2001'
B g2 = '0DB8'
C g3 = '00GF'
Line C — Hexadecimal digits only go from 0 to 9 and A to F. G is not a valid hex digit, so the group should be '00FF'.
Question 3
A # first four groups
B part = '2001-0DB8-0000-0042'
C print(part.split(':'))
Line B — The groups in an IPv6 address are separated by colons, not hyphens. The line should be part = '2001:0DB8:0000:0042'.
Question 4
A version = 6
B groups = 8
C digits = 4
D print('IPv6 is 32 bits')
Line D — An IPv6 address is 128 bits long. 32 bits is the size of an IPv4 address. The line should print 'IPv6 is 128 bits'.
Question 5
A groups = 4
B digits = 4
C print(groups, 'x', digits)
Line A — An IPv6 address has eight groups, not four. The line should be groups = 8.

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