VLSM Example

Given

An organization has been assigned the network number 140.25.0.0/16

and it plans to deploy VLSM. Figure 21 provides a graphic display of

the VLSM design for the organization. 

F I G U R E   2 1 .   A d d re s s   S t r a t e g y   f o r   V L S M   E x a m p l e

The first step of the subnetting process divides the base network

address into 16 equally sized address blocks. Then Subnet #1 is divided

into 32 equally sized address blocks and Subnet #14 is divided into 16

equally sized address blocks. Finally, Subnet #14 14 is divided into

eight equally sized address blocks. 

Define the 16 Subnets of 140.25.0.0/16

The first step in the subnetting process divides the base network

address into 16 equally sized address blocks, as illustrated in Figure 22. 

F I G U R E   2 2 .   S i x t e e n   S u b n e t s   f o r   1 4 0 . 2 5 . 0 . 0 / 1 6

Since 16 = 24, four bits are required to identify each of the 16 subnets.

This means that the organization needs four more bits, or a /20, in the

extended network prefix to define the 16 subnets of 140.25.0.0/16.

Each of these subnets represents a contiguous block of 212 (or 4,096)

network addresses. 

U N D E R S TA N D I N G   I P   A D D R E S S I N G

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