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Subnetting examples (class A, B and C)

Compute the subnet mask, number of subnets and number of hosts in each subnet, in each of the given scenarios.

Scenario 1:
Required Number of Networks: 80
Minimum Number of Hosts: 3000
Network Address: 10.0.0.0

Scenario 2:
Required Number of Networks: 20
Minimum Number of Hosts: 800
Network Address: 141.15.0.0

Scenario 3
Required Number of Networks: 5
Minimum Number of Hosts: 25
Network Address: 198.171.10.0

Solution Preview

If we breakup the 32 bit IP address as (net : subnet : host), then

number of hosts in each subnet = (2 ^ number_of_host_bits) - 2 , as host numbers consisting of all 0 and all 1 bits are reserved.

Similar restriction is also applied to subnets by older standards, however recent standards do allow use of all 0 bits and all 1 bits subnets. Hence,

number of subnets = (2 ^ number_of_subnet_bits) , as per recent standards.
number of subnets = (2 ^ number_of_subnet_bits) - 2 , as per older standards.

This answer is following recent standards.

Scenario ...

Solution Summary

Solution shows stepwise computations with detailed explanations, following which, the reader should be able to solve similar problems easily. It also has a brief comment about recent vs older subnetting standards.

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