how calculate the number of ip addresses in a range?

[Peter Wemm]

On Thu, Aug 8, 2013 at 12:04 AM, s m <sam.gh1986 at gmail.com> wrote:
> hello guys,
>
> i have a question about ip addresses. i know my question is not related to
> freebsd but i googled a lot and found nothing useful and don't know where i
> should ask my question.
>
> i want to know how can i calculate the number of ip addresses in a range?
> for example if i have 192.0.0.1 192.100.255.254 with mask 8, how many ip
> addresses are available in this range? is there any formula to calculate
> the number of ip addresses for any range?
>
> i'm confusing about it. please help me to clear my mind.
> thanks in advance,

My immediate reaction is.. is this a homework / classwork / assignment?

Anyway, you can think of it by converting your start and end addresses
to an integer.  Over simplified:

$ cat homework.c
main()
{
int start =  (192 << 24) | (0 << 16) | (0 << 8) | 1;
int end =  (192 << 24) | (100 << 16) | (255 << 8) | 254;
printf("start %d end %d range %d\n", start, end, (end - start) + 1);
}
$ ./homework
start -1073741823 end -1067122690 range 6619134

The +1 is correcting for base zero. 192.0.0.1 - 192.0.0.2 is two
usable addresses.

I'm not sure what you want to do with the mask of 8.

You can also do it with ntohl(inet_addr("address")) as well and a
multitude of other ways.

-- 
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
UTF-8: for when a ' just won\342\200\231t do.
<brueffer> ZFS must be the bacon of file systems. "everything's better with ZFS"