250+ TOP MCQs on Classful Addressing and Answers

Network Security Multiple Choice Questions on “Classful Addressing”.

1. Each block in class A contains _____________ addresses.
a) 2¹⁶
b) 2²⁴
c) 2⁸
d) 2¹⁴

Answer: b
Clarification: Each block in class A contains 2²⁴ addresses.

2. Each block in class B contains __________ addresses.
a) 2⁸
b) 2²⁴
c) 2¹⁴
d) 2¹⁶

Answer: d
Clarification: Each block in class B contains 2¹⁶ addresses.

3. Number of Blocks in class B are –
a) 2¹²
b) 2¹⁶
c) 2¹⁴
d) 2¹⁸

Answer: c
Clarification: Number of Blocks in class B are 2¹⁴.

3. Number of Blocks in class C are –
a) 2¹²
b) 2¹⁶
c) 2¹⁴
d) 2¹⁸

Answer: c
Clarification: Number of Blocks in class C are 2¹⁴.

4. Percent of addresses occupied by Class D?
a) 50 %
b) 25 %
c) 6.25 %
d) 12.5 %

Answer: c
Clarification: Class D has 2²⁸ addresses in total.

5. Which of the following does not have a Net ID and Host ID?
a) Class A
b) Class B
c) Class C
d) Class D

Answer: d
Clarification: Class D is the multicast address class. It does not have Net ID and Host ID fields.

6. Which Class is reserved for future use?
a) A
b) B
c) D
d) None of the Mentioned

Answer: d
Clarification: Class E is reserved for future use.

7. Number of Blocks in class C are –
a) 2⁷
b) 2⁸
c) 2¹⁴
d) 2⁹

Answer: a
Clarification: Number of Blocks in class A are 2⁷.

8. What is the size of the Host ID in Class C?
a) 24 bits
b) 16 bits
c) 8 bits
d) 14 bits

Answer: c
Clarification: The size of the Host ID in Class C is 8 bits.

An address in a block is given as 180.8.17.9. Find the number of addresses in the block, the first address, and the last address.

9. Address of the block is –
a) 2¹⁴
b) 2¹⁶
c) 2⁸
d) 2²⁴

Answer: b
Clarification: Since 180 is between 128 and 191, it is class B address n=16.
N = 2^(32-n) = 2¹⁶ = 65,536.

10. First Address is –
a) 180.8.0.0
b) 180.7.64.0
c) 180.8.1.256
d) 180.12.0.0

Answer: a
Clarification: Keep the leftmost 16 bits and set the rightmost 16 bits all to 0s. First address = 180.8.0.0, in which 16 is the value of n.

11. Last Address is –
a) 180.8.255.255.
b) 180.8.255.0.
c) 180.12.0.255.
d) 180.9.255.255.

Answer: a
Clarification: Keep the leftmost 16 bits and set the rightmost 16 bits all to 1s. Last address = 180.8.255.255.

12. A router receives a packet with the destination address 132.7.21.84. Find the network address of the packet.
a) 1.32.7
b) 132.7
c) 13.27
d) 21.84

Answer: b
Clarification: 132 is between 128 and 191, so it is Class B address i.e. n=16-bit. Therefore,
Network address 132.7
Host address 21.84.