Subnetting Questions 13 | Find the Subnet Mask, Network and host

Subnetting Questions 13

You are working on a class C network. You are required to configure it for five subnets, each of which will support 25 nodes. What subnet should you use?

Solutions

Let’s count the number of hosts first,

A/Q we need minimum 25 hosts on each network. It means, we have to reserved 5 bits for the host.

The formula of counting the host is

2ⁿ –  2 (n indicates the number of host bits, substracted to 2 because on every network first and last address is always reserved for the network and broadcast ID)

= 2ⁿ –  2

= 2⁵ – 2

= 32- 2 = 30 (You have 30 host on each network)

Let’s count the number of Networks

The formula for counting the number of networks is,

2ⁿ (n indicates the number of reserved network bits)

= 2³

= 8 (You will have minimum 8 bits)

Let’s find the subnet mask

(11111111.11111111.11111111.11100000)

(2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵)

Therefore the subnet mask is 255.255.255.224