Subnetting Questions 1 | Find the Subnet Mask from the IP Address

Subnetting Question 1

You have a class A network address 10.0.0.0 with 40 subnets, but you are required to add 60 new subnets very soon. You would like to still allow for the largest possible number of host IDs per subnet. Which subnet mask should you assign?

1. 255.240.0.0
2. 255.248.0.0
3. 255.252.0.0
4. 255.254.0.0

Solution:

Hence, 10.0.0.0 is a Class A IP Address and by default, its network bit is 8 and host bit is 24.

A/Q there are 40 Subnets available and we need another 60 subnets.

It means the total subnet we need is 40+60=100

So, we have to borrow 7 bits from the host (2⁷ = 128 Subnets). It is the number of subnets with the maximum host.

Now, let’s find the subnet mask

Count the value of all the bits borrowed from the host. Hence we have borrowed 7 bits so, (2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹) = 254

Therefore, the new subnet mask you will get is 255.254.0.0.

Find the Subnet Mask for 100 Subnets with maximum host

Class A Subnetting video Tutorial

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