Complete the following steps to practice calculating a Supernet: 1. Starting wit
ID: 3689966 • Letter: C
Question
Complete the following steps to practice calculating a Supernet:
1. Starting with the network ID 192.16.20.0/24, what is the default Class C subnet mask for this network? Write this information both in decimal and in binary.
2. How many additional network bits must be used for host information in order to have about 2000 hosts per supernet? Use the same formula you learned for calculation number of host on a subnet. Write the new supernet mask in binary and in decimal notation.
3. What is the CIDR notation for the network ID now?
Explanation / Answer
1.
Consider the network ID 192.16.20.0/24, the default class C subnet mast for this network is as follows:
Subnet mask in decimal = 255.255.255.0
Subnet mask in binary = 11111111.11111111.11111111.00000000
2.
To have 255 host per supernet, 24 bit will be needed as network ID. If it needed 2000 host per supernet, in this case it must borrow some bits from the network id. Since to have 2000 host per supernet there are 11 bits will be needed.
We have already 8 bits to store the host information’s. It means to store the 2000 host per supernet, 3 addition bits must be needed from network id.
Thus, the 3 additional bits must be used for host information to have about 2000 host per supenet.
The new supenet mask for this supenet is as follows:
Decimal = 255.255.248.0
Binary = 11111111.11111111.11111000.00000000
3.
CIDR notation for the network id is,
Decimal = 255.255.248.0/21
Binary = 11111111.11111111.11111000.00000000/21