I am trying to get a subnet of 32 networks from 172.26.16.0/19 will it give the range from 172.26.16.0 till 172.26.47.0 ?
Everytime that I am using the websites for subnet calculator for 172.26.16.0/19 ,it will give the range starting from 172.26.0.0 till 172.26.31.0 and the issue is that from .0 till .15 range is already used.
Many thanks for your supports.
Regards, Ethem
I am trying to get a subnet of 32 networks from 172.26.16.0/19
Unless I misunderstood what you want, you can't do that because 172.26.16.0/19 is not a correct network address.
See the notation in binary:
10101100.00011010.00010000.00000000
=====================--------------
Network part Host part
In short, the host part is not all zeros, so there is something wrong with your numbers.
Variable Length Subnet Masking has granted us, as network admins, great flexibility in using, essentially arbitrary prefix lengths for subnets. For example, being able to take the network 10.1.1.0/25 and decide to change that prefix to a /24 on a whim is has become very convenient and, frankly, essential in today's ever changing networks.
That, however, does not grant us the ability to start and/or end a subnet at an arbitrary place within a given range of addresses. Because even though VLSM grants us flexibility in network numbering, the problem of network boundaries remains, which bleeds over from VLSM to CIDR, actually. Consider the following...
Specifying a subnet of 10.1.1.0/28 is very clear...
The same would not be true if one were to try to define a network of 10.1.1.6/28, the idea being 10.1.1.7 as the first usable address, with 10.1.1.21 as a broadcast. The problem is that "subnet" (in quotes because it's really not properly defined) straddles two /28's: 10.1.1.0/28 and 10.1.1.16/28. This is, essentially what you're trying to do, except with supernets.
The problem you're running into is 172.26.16.0, while indeed part of the larger /19 supernet, nevertheless belongs in 172.26.16.0/20 (172.26.16.0 - 172.26.31.255), which is the second half of 172.26.0.0/19, the first half being 172.26.0.0/20. So, to re-illustrate...
172.26.0.0/20 (16 Class Bs) and 172.26.16.0/20 (16 Class Bs) form 172.26.0.0/19 (32 Class Bs), ranging from 172.26.0.0 - 172.26.31.255. The other end of your desired range (172.26.47.0) is actually the tail end of 172.26.32.0/20 (172.26.32.0 - 172.26.47.255), which is in the "other" /19 of 172.26.0.0/18.
All this to say that while you are talking about IP supernets that are technically contiguous, you have to, nevertheless, allocate them within the boundaries in which they fall when /18s split into /19s, etc. In other words, say I assign you a /18 supernet and you want to utilize two /20s from it. The /18 breaks in half to form two /19s and each of those /19s break to form two /20s, so you end up with four /20s from the two /19s from the one /18. When it comes time to use the /20's however, and you're in the scenario where just one /20 isn't going to be adequate and you commit to using an additional /20, it has to come from the same parent /19. You cannot take a /20 from one /19 and a /20 from the other /19 and span a subnet between them, even if one does begin where the other ended, because they are from different parent networks, or supernets.
I hope this helps a little.
