Subnetting Questions 42 | Find the maximum number of Subnets

Subnetting Questions 42

Enter the maximum number of valid subnets and usable hosts per subnet that you can get from the network 172.21.0.0 255.255.248.0

Solution

Hence, the IP Address starts from 172 it indicates it is a Class B Address. and in Class B Address 16 bits are reserved for the network and 16 bits are reserved for the host.

First of all, we have to find the number of network and host bits.

A/Q the subnet mask is

255.255.248.0

(2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³) . (0)

11111111 . 11111111 . 11111000 . 00000000

Hence, the IP Address is Class B. we have borrowed 5 bits from the third octet to make it (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ = 248) and the remaining 11 bits are host.

Let’s find the number of Subnets

The formula for calculating the number of subnets is

2ⁿ (n is the number of borrowed network bits)

= 2⁵

= 32

Therefore, the total number of the subnet is 32.

Let’s find the number of the host on each network

The formula for calculating the number of hosts is

2ⁿ – 2 (n is the number of host bits, subtracted 2 because on every network the first IP Address is reserved for the network ID and last IP Address is reserved for the broadcast address)

2¹¹ – 2

= 2048 – 2

= 2046 

Therefore, there is 2046 available host on each network.