how calculate the number of ip addresses in a range?

[Damien Fleuriot]

On 10 Aug 2013, at 01:17, Peter Wemm <peter at wemm.org> wrote:

> On Fri, Aug 9, 2013 at 4:07 PM, Kimmo Paasiala <kpaasial at gmail.com> wrote:
>> On Sat, Aug 10, 2013 at 1:44 AM, Peter Wemm <peter at wemm.org> wrote:
>>> On Fri, Aug 9, 2013 at 9:34 AM, Fleuriot Damien <ml at my.gd> wrote:
>>>> 
>>>> On Aug 8, 2013, at 10:27 AM, Peter Wemm <peter at wemm.org> wrote:
>>>> 
>>>>> 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.
>>>> 
>>>> 
>>>> Hold on a second, why would you correct the base zero ?
>>>> It can be a valid IP address.
>>> 
>>> There is one usable address in a range of 10.0.0.1 - 10.0.0.1.
>>> Converting to an integer and subtracting would be zero.  Hence +1.
>>> 
>>> --
>> 
>> To elaborate on this, for every subnet regardless of the address/mask
>> combination there are two unusable addresses: The first address aka
>> the "network address" and the last address aka the "broadcast
>> address". There may be usable address in between the two that end in
>> one of more zeros but those addresses are still valid. Some operating
>> systems got this horribly wrong and marked any address ending with a
>> single zero as invalid, windows 2000 was one of them.
>> 
>> -Kimmo
> 
> If we go back to the orignal question: "if i have 192.0.0.1
> 192.100.255.254 how many ip addresses are available in this range?"
> They're all in the same 192.0.0.0/8.  Broadcast or sink addresses
> don't factor into it.
> 
> -- 
> 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"

Peter,

The original question is "how to calculate a range", nobody said it should be a /24, that was merely an example.