Mental Block - quick math Q

[TheExcession]

IP Subnets and Hosts and Subnet bits.

My minds gone blank.

Given that
2^(number_of_bits) – 2 = number_of_hosts

I want to get a value for number_of_bits given that I know the number of hosts.

what is the inverse of 2^n

feeling very dumb - thanks for an answer.

best
Ex

[Hamster]

Blimey

How can you feel dumb for not knowing the answer to this. I don't even understand the question............

KS

[TheExcession]

ok - given

2^y=n
y=??? when n=256

eg

y=2 -> 2^2 = 4
y=3 -> 2^3 = 8
y=4 -> 2^4 = 16
y=5 -> 2^5 = 32

if for example I tell you the answer is 64 then the question was y=6 easy to spot but what is the question when the answer is 256? Obviously its 8 but why? and what is the question when the answer is 1073741824?

best
Ex

>> Edited by TheExcession on Thursday 14th October 14:28

[AlexHancock]

The inverse is ^ 1/n.

So if n is 2

The inverse of 2 ^ 2 is 2 ^ 0.5

Edited for Ex

2 ^ 256 is 1.1579208923731619542357098500869e+77

So to get back

1.1579208923731619542357098500869e+77 ^ 0.00390625

where 0.00390625 is 1/256

>> Edited by AlexHancock on Thursday 14th October 14:36

[TheExcession]

knew it was in my head somewhere

number bits = [log (hosts + 2) ]/ log 2

[AlexHancock]

Good stuff - I suddenly realised I was giving you the wrong answer! It was more interesting than my current development though...

[TheExcession]

AlexHancock said:

Good stuff - I suddenly realised I was giving you the wrong answer! It was more interesting than my current development though...

cheers -

Good old Napier - I'd forgotten all about him and his bones.

best
Ex

[Pigeon]

Shift it right until it's zero, and count the number of shifts.