Spotting an invalid IPv4 address
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which of these is a valid IPv4 address?
2. Why is 192.168.1 an invalid IPv4 address?
3. Which address is invalid?
4. Is 255.255.255.255 a valid IPv4 address?
5. Which address is invalid because of a letter?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1256.10.4.7 | AThe second group is a letter. Groups must be numbers from 0 to 255, so the address is invalid. | |
| 2192.168.1 | BInvalid: it has only three groups instead of exactly four | |
| 3An IPv4 address with more than four groups is invalid | C10.0.0.1.5 | |
| 4Every group in a valid IPv4 address must be a whole number from 0 to 255 | D172.16.254.1 | |
| 510.-5.2.1 | EThe second group is a negative number. Groups cannot be below 0, so the address is invalid. | |
| 610.a.2.1 | FInvalid: the first group is 256, which is above the maximum of 255 |
C
Definitions
invalid IPv4 address
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
256.1.1.1 is invalid: 256 is above ___
2.
192.168.1 is invalid: 3 groups, need _
3.
10.-5.2.1 is invalid: -5 is below _
4.
10.a.2.1 is invalid: a group must be a ______
5.
IF group < 0 __ group > 255 THEN
OUTPUT "Invalid"
ENDIF
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
Router: 192.168.0.1
B
Laptop: 192.168.0.12
C
Printer: 192.168.0.256
D
Phone: 192.168.0.31
Question 2
A
Server: 10.0.0
B
PC1: 10.0.0.6
C
PC2: 10.0.0.7
Question 3
A
Lab network
B
PC1: 172.16.4.10
C
PC2: 172.16.4.11
D
PC3: 172.16.4.12.5
Question 4
A
Switch: 192.168.5.1
B
Camera: 192.168.B.40
C
Tablet: 192.168.5.41
Question 5
A
Gateway: 10.1.1.1
B
Guest1: 10.1.1.8
C
Guest2: 10.-1.1.9
Answer Key
Spotting an invalid IPv4 address
Section A: Quick Questions
Q1
A — 192.168.0.1
Q2
A — It has only three groups instead of four
Q3
B — 10.0.0.0.5
Q4
B — Yes, because 255 is the highest allowed group value
Q5
A — 172.16.a.4
Section B: Match the Pairs
Q1
256.10.4.7 → Invalid: the first group is 256, which is above the maximum of 255
Q2
192.168.1 → Invalid: it has only three groups instead of exactly four
Q3
An IPv4 address with more than four groups is invalid → 10.0.0.1.5
Q4
Every group in a valid IPv4 address must be a whole number from 0 to 255 → 172.16.254.1
Q5
10.-5.2.1 → The second group is a negative number. Groups cannot be below 0, so the address is invalid.
Q6
10.a.2.1 → The second group is a letter. Groups must be numbers from 0 to 255, so the address is invalid.
Section C: Definitions
Q1
invalid IPv4 address — An address without exactly four groups, or with a group outside 0 to 255. Examples: 256.1.1.1 (too big), 192.168.1 (too few groups), 10.-5.2.1 (negative) and 10.a.2.1 (letter).Section D: Fill in the Blanks
Q1
256.1.1.1 is invalid: 256 is above 255Q2
192.168.1 is invalid: 3 groups, need 4Q3
10.-5.2.1 is invalid: -5 is below 0Q4
10.a.2.1 is invalid: a group must be a numberQ5
IF group < 0 OR group > 255 THEN
OUTPUT "Invalid"
ENDIFSection E: Spot the Error
Q1
C — Each group in an IPv4 address must be from 0 to 255. 256 is too big, so the address is invalid. It should be a value such as 192.168.0.20.
Q2
A — An IPv4 address needs exactly four groups. 10.0.0 only has three, so it is invalid. It should be 10.0.0.5.
Q3
D — This address has five groups. IPv4 allows exactly four, so it is invalid. It should be 172.16.4.12.
Q4
B — Each IPv4 group must be a number from 0 to 255. A letter such as B is not allowed. It should be 192.168.5.40.
Q5
C — A group cannot be negative because the range starts at 0. 10.-1.1.9 is invalid. It should be 10.1.1.9.