Shortening an IPv6 address

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. An IPv6 group is 0A00. Which is its shortened form with leading zeros dropped?

A A00

B A

2. How many times can :: appear in one IPv6 address?

A Once for every run of zero groups

B Only once

3. Which is a valid shortened IPv6 address?

A 2001::db8::1

B 2001:db8::1

4. The address 2001:db8::1 is expanded back to eight groups. What does :: stand for?

A Five groups of 0000

B Three groups of 0000

5. What can be replaced with :: in an IPv6 address?

A A run of groups that are all zeros

B Any group that contains a zero

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
10db8 -> db8		ADrops the leading zero from a group, so the group is written with fewer digits
22001:db8::1		Bfe80:0:0:0:0:0:0:1 -> fe80::1
3Replace one run of all-zero groups with :: to shorten the address		CExpands to 2001:0db8:0000:0000:0000:0000:0000:0001, with :: standing for five all-zero groups
4Expand a shortened address back to eight groups by filling :: with zero groups		D::1 = 0000:0000:0000:0000:0000:0000:0000:0001
52001::db8::1		EOnly leading zeros can be dropped. The zero at the end of the group is part of the value, so d8 is a different number.
60d80 -> d8		FThe :: is used twice. It can only appear once, otherwise nobody can tell how many zero groups each one replaces.

Definitions

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Full: 2001:0db8:0000:0000:0000:0000:0000:0001 Short: 2001:db8__1

Full: fe80:0000:0000:0000:0202:b3ff:fe1e:8329 Short: fe80::___:b3ff:fe1e:8329

Short: 2001:db8::ff00:42:8329 Full: 2001:0db8:0000:0000:0000:ff00:____:8329

Rule: :: can be used only ____ per address

Address: fe80::1 Groups written out: 2 of 8 :: replaces _ groups of 0000

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A group = 00a4

B leading zeros = 2

C drop all leading zeros

D short = 0a4

Question 2

A group = 0000

B short = nothing

C a group is never left empty

Question 3

A group = 0d00

B short = d

C trailing zeros must stay

Question 4

A addr = 2001:db8:0:0:1:0:0:2

B zero runs: 0:0 and 0:0

C use :: on both runs

D short = 2001:db8::1:0:0:2

Question 5

A short = fe80::1

B groups shown = 2

C zero groups hidden = 5

D full has 8 groups

Answer Key

Shortening an IPv6 address

Section A: Quick Questions

A — A00

B — Only once

B — 2001:db8::1

A — Five groups of 0000

A — A run of groups that are all zeros

Section B: Match the Pairs

0db8 -> db8 → Drops the leading zero from a group, so the group is written with fewer digits

2001:db8::1 → Expands to 2001:0db8:0000:0000:0000:0000:0000:0001, with :: standing for five all-zero groups

Replace one run of all-zero groups with :: to shorten the address → fe80:0:0:0:0:0:0:1 -> fe80::1

Expand a shortened address back to eight groups by filling :: with zero groups → ::1 = 0000:0000:0000:0000:0000:0000:0000:0001

2001::db8::1 → The :: is used twice. It can only appear once, otherwise nobody can tell how many zero groups each one replaces.

0d80 -> d8 → Only leading zeros can be dropped. The zero at the end of the group is part of the value, so d8 is a different number.

Section C: Definitions

:: — Replaces one run of all-zero groups in an IPv6 address, and can be used only once. Leading zeros in each group can also be dropped, e.g. 0db8 becomes db8.

Section D: Fill in the Blanks

Full: 2001:0db8:0000:0000:0000:0000:0000:0001
Short: 2001:db8::1

Full: fe80:0000:0000:0000:0202:b3ff:fe1e:8329
Short: fe80::202:b3ff:fe1e:8329

Short: 2001:db8::ff00:42:8329
Full: 2001:0db8:0000:0000:0000:ff00:0042:8329

Rule: :: can be used only once per address

Address: fe80::1
Groups written out: 2 of 8
:: replaces 6 groups of 0000

Section E: Spot the Error

D — Both leading zeros must be dropped, so 00a4 becomes a4. Dropping only one zero leaves 0a4.

B — A group of all zeros shortens to a single 0, not to nothing. Only :: can stand in for whole zero groups.

B — Only leading zeros can be dropped. The two zeros after the d are trailing zeros, so 0d00 becomes d00.

C — The :: can be used only once in an address. If it were used twice, nobody could tell how many zero groups each one hides. It should say to use :: on only one run.

C — A full address has 8 groups and 2 are shown (fe80 and 1), so :: hides 8 - 2 = 6 zero groups, not 5.