Subnet Self-Doubt

Question

If there are n bits available for subnet, how many sub-nets are possible ?

Comments

$2^{n}-1$?

All zeros is network id.

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@zxy123 What about Broadcast Address?

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$2^n-2$ then?

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Yes TRUE but in many cases, I have seen $2^n$ also. I have the same doubt.

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Till gate level if nothing specified then go for 2^n subnet and if host  : n bit then 2^n – 2 host