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Networking Fundamentals · Foundational

Subnetting

Dividing a larger IP network into smaller subnets by borrowing host bits for the network portion.

Definition

Subnetting improves address efficiency, reduces broadcast domain size, and allows security and routing boundaries between groups. Each borrowed bit doubles the number of subnets and halves the hosts per subnet. Exams require fast calculation of network, broadcast, first and last host, and number of subnets or hosts.

Example

Dividing 192.168.10.0/24 into four /26 subnets gives 0, 64, 128 and 192 as network addresses.

Exam tip

Practice speed: block size = 256 minus the interesting mask octet.

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