UGC NET Computer Science Questions Set 2 | computer networks | IP addressing

Question 1

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1. An organization has a Class B Network and need to form subnet for 64 departments
what would be the appropriate Subnet Mask

1. 1. 255.255.0.0
2. 2. 255.255.64.0
3. 3. 255.255.128.0
4. 4. 255.255.252.0

Explanation Question 1
In class B network, 16 bits are used for Network ID and 16 bits are for Host ID part. In subnetting the bits are borrowed from Host portion.

Here, we want 64 subnets. so, we have to borrow 6 bits from host id part because 2⁶ = 64 number of subnets we require. Subnet mask will have total 16 + 6 bits as continuous 1's. in network id and subnet id part.

Binary form of subnet mask is : 11111111.11111111.11111100.00000000
Decimal form of subnet mask is : 255.255.252.0

So, option (4) is the correct answer.

Question 2

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2. Consider a class A, Class B and Class C network.
Consider the given IP address and subnet mask
IP Address : 150.157.100.70
Subnet Mask : 255.255.224.0
What is the address of the network in which host belong to

1. 1. 150.157.96.70
2. 2. 150.157.96.0
3. 3. 150.157.48.0
4. 4. None

Explanation Question 2

If any given IP address performs bit wise AND operation with the subnet mask, then you get the network id of the subnet to which the given IP belongs.

If IP address = 150.157.100.70 (convert it into binary form)
Binary form of IP address is : 10010110.10011101.01100100.01000110

IP address	= 10010110.10011101.01100100.01000110
Subnet mask	= 11111111. 11111111. 11100000.00000000
Bit Wise AND	= 10010110.10011101.01100000.00000000

Binary form of network address is : 10010110.10011101.01100000.00000000
Deciaml form of network address is : 150.157.96.0
Therefore, Nid = 150.157.96.0

So, option (2) is the correct answer.

Question 3

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3. Subnet mask for a particular network is 255.255.31.0 then tell about Which pairs of IP addresses could belong to this network ?

1. 1. 172.57.88.62 and 172.56.87.23.2
2. 2. 10.35.28.2 and 10.35.29.4
3. 3. 191.203.31.87 and 191.234.31.88
4. 4. 128.8.129.43 and 128.8.161.55

Explanation Question 3

If IP₁ and IP₂ belongs to same network, we must have
IP₁ BITWISE-AND "Subnet mask" = Network Address
= IP₂ BITWISE-AND "Subnet mask"

Out of the 4 options, only option D matches.
128.8.129.43 BITWISE-AND 255.255.31.0 = 128.8.1.0
128.8.161.55 BITWISE-AND 255.255.31.0 = 128.8.1.0

Both addresses belongs to same network.
You can check rest of the options.

Question 4

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4. If a class B IP address has the subnet mask 255.255.248.0 then How many maximum host will be possible in the network?

1. 1. 1022
2. 2. 1023
3. 3. 2046
4. 4. 2047

Explanation Question 4

Binary form of subnet mask of 255.255.248.0 is : 11111111.11111111.11111000.00000000 From above binary form of subnet mask. you can say that subnet mask of 255.255.248.0 will have a 21 bits network id and having 11 host bits.

Given the subnet mask, you can calculate the number of hosts using the formula below:
2^h - 2, where h is the number of host bits (in simple terms the number of zeros in the subnet mask)

This network will have total 2048 (2¹¹ ) hosts. The first address is the network address, while the last one is the broadcast ip address, thus we subtract 2 addresses, then there can be a maximum 2046 hosts.

So, option (3) is the correct answer.

Question 5

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5. If a Class B IP address is split into subnet and 6 bits are used for subnet. What is maximum number of subnet and hosts per subnet ?

1. 1. 62 subnets and 262142 hosts
2. 2. 64 subnets and 262142 hosts
3. 3. 62 subnets and 1022 hosts
4. 4. 64 subnets and 1024 hosts

Explanation Question 5

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Question 6

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6. Consider the IP address 25.193.155.233. How many bits are there in Network Id and Host Id ?

1. 1. 24 bit for NID, 8 bits for HID
2. 2. 8 bit for NID, 24 bits for HID
3. 3. 16 bit for NID, 16 bits for HID
4. 4. none

Explanation Question 6

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Question 7

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7. Find the wrong statement among the following related to Subnetting?

1. 1. It can be applied only for single network
2. 2. It is used to improve security
3. 3. Here, bits are borrowed from network ID portion
4. 4. Here, bits are borrowed from host ID portion

Explanation Question 7

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Question 8

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8. Logical addressing system is used by which device ?

1. 1. Hub
2. 2. Switch
3. 3. bridge
4. 4. Router

Explanation Question 8

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Question 9

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9. Which of the following is not true about Supernetting?

1. 1. It is used to increase security
2. 2. It is applicable for two or more networks
3. 3. Bits are borrowed from network ID portion
4. 4. It is used to improve flexibility of IP address allotment

Explanation Question 9

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Question 10

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10. What is the network ID of the IP address 225.100.123.71?

1. 1. 225.100.123.70
2. 2. 225.100.123.72
3. 3. 225.100.123.75
4. 4. It does not has any network ID

Explanation Question 10

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