Class A Subnet Masks

Question 1

255.0.0.0

Answer 1

Class A default network mask
8 network bits, 24 host bits (none borrowed for submitting)

1 network, 16,777,214 hosts

Question 2

255.128.0.0

Answer 2

9 network bits (1 bit borrowed), 23 host bits

2 subnets, 8,388,606 hosts per subnet

Question 3

255.192.0.0

Answer 3

10 network bits (2 borrowed), 22 host bits

4 subnets, 4,194,302 hosts per subnet

Question 4

255.224.0.0

Answer 4

11 network bits (3 borrowed), 21 host bits

8 subnets, 2,097,150 hosts per subnet

Question 5

255.240.0.0

Answer 5

12 network bits (4 borrowed), 20 host bits

16 subnets, 1,048,574 hosts per subnet

Question 6

255.248.0.0

Answer 6

13 network bits (5 borrowed), 19 host bits

32 subnets, 524,286 hosts per subnet

Question 7

255.252.0.0

Answer 7

14 network bits (6 borrowed), 18 host bits

64 subnets, 262,142 hosts per subnet

Question 8

255.254.0.0

Answer 8

15 network bits (7 borrowed), 17 host bits

128 networks, 131,070 hosts per subnet

Question 9

255.255.0.0

Class A

Answer 9

16 network bits (8 borrowed), 16 host bits

256 subnets, 65,534 hosts per subnet

Question 10

255.255.128.0

Class A

Answer 10

17 network bits (9 borrowed), 15 host bits

512 subnets, 16,382 hosts per subnet

Question 11

255.255.192.0

Class A

Answer 11

18 network bits (10 borrowed), 14 host bits

1,024 subnets, 16,382 hosts per subnet

Question 12

255.255.224.0

Class A

Answer 12

19 network bits (11 borrowed), 13 host bits

2,048 subnets, 8,190 hosts per subnet

Question 13

255.255.240.0

Class A

Answer 13

20 network bits (12 borrowed), 12 host bits

4,096 subnets, 4,094 hosts per subnet

Question 14

255.255.248.0

Class A

Answer 14

21 network bits (13 borrowed), 11 host bits

8,192 subnets, 2,046 hosts per subnet

Question 15

255.255.252.0

Class A

Answer 15

22 network bits (14 borrowed), 10 host bits

16,384 subnets, 1,022 hosts per subnet

Question 16

255.255.254.0

Class A

Answer 16

23 network bits (15 borrowed), 9 host bits

32,768 subnets, 510 hosts per subnet

Question 17

255.255.255.0

Class A

Answer 17

24 network bits (16 borrowed), 8 host bits

65,536 subnets, 254 hosts per subnet

Question 18

255.255.255.128

Class A

Answer 18

25 network bits (17 borrowed), 7 host bits

131,072 subnets, 126 hosts per subnet

Question 19

255.255.255.192

Class A

Answer 19

26 network bits (18 borrowed), 6 host bits

262,144 subnets, 62 hosts per subnet

Question 20

255.255.255.224

Class A

Answer 20

27 network bits (19 borrowed), 5 host bits

524,288 subnets, 30 hosts per subnet

Question 21

255.255.255.240

Class A

Answer 21

28 network bits (20 borrowed), 4 host bits

1,048,576 subnets, 14 hosts per subnet

Question 22

255.255.255.248

Class A

Answer 22

29 network bits (21 borrowed), 3 host bits

2,097,152 subnets, 6 hosts per subnet

Question 23

255.255.255.252

Class A

Answer 23

30 network bits (22 borrowed), 2 host bits

4,194,302 subnets, 2 hosts per subnet

Question 24

255.255.255.254

Class A

Answer 24

31 network bits (23 borrowed), 1 host bit

8,388,608 subnets, 2 IP addresses; this is described in RFC 3021 as a point-to-point link. Both IP addresses are used as hosts, and broadcasts are limited.