computer network - Class A Subnetting

Class A Subnetting:

As we know the Class A network address has 24 bits available for host addressing. This means we can use up to 22 bits for subnetting.

The process of subnetting a Class A network is pretty much the same as it is for a Class B.

Let’s start:
               Example as follows
               10.0.0.0 = Network Address
               255.128.0.0 = Subnet Mask
               (11111111.10000000.00000000.00000000)

Now we are applying top 5 formulas to find out subnets, hosts, valid subnets, broadcast address.

  • How many subnets?

Formula is: 2x = number of subnets. x is the number of masked bits, or the 1s. Because 128 is 1 bit on (10000000), the answer is 21=2


  • How many hosts per subnet?

Formula is: 2Y-2 = number of hosts per subnet. y is the number of unmasked bits, or the 0.

We have 23 host bits off (10000000.00000000.00000000), so the equation is 223-2 = 83,88,606 hosts (83,88,608-2).


  • What are the valid subnets?

Formula is: 256-subnet mask = block size, or increment number.

So, 256-128=128. Remember, we'll start at zero and count in our block size, so our subnets are 0, 128.


Class A Subnet Table
 Like wise you can make subnetting of all class A IP addresses.