yes..! looks correct

but discussion over https://gateoverflow.in/1265/gate2007-67-isro2016-72, confuses whether to subtract 2 or not!

new and old conventions :(

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Consider a class $\mathbf B$ network subnet mask for a network is $255.255.255.240$. The number of hosts per subnet is:

(a)$2^2-2$

(b)$2^4-2$

(c)$16$

(d)$2^3-2$

I am trying to do it this way:

NID + SID = Number of 1’s

In class B network, NID has: 16 Ones.

$\therefore 16 + SID = 28\\\Rightarrow \text{SID} = 12$

Now, $16 + 12 = 28$ bits are fixed.

On substituting, all $0’\text{s}$ in rest $4$ parts.

Number of SIDs $=2^{4}-2$

Am I right?

(a)$2^2-2$

(b)$2^4-2$

(c)$16$

(d)$2^3-2$

I am trying to do it this way:

NID + SID = Number of 1’s

In class B network, NID has: 16 Ones.

$\therefore 16 + SID = 28\\\Rightarrow \text{SID} = 12$

Now, $16 + 12 = 28$ bits are fixed.

On substituting, all $0’\text{s}$ in rest $4$ parts.

Number of SIDs $=2^{4}-2$

Am I right?

yes..! looks correct

but discussion over https://gateoverflow.in/1265/gate2007-67-isro2016-72, confuses whether to subtract 2 or not!

new and old conventions :(

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