Re: CIDR Utilization

[Theodore Baschak <theodore () ciscodude net>]

> On Oct 30, 2015, at 7:51 PM, John Steve Nash <john.steve.nash () gmail com> wrote:
>
> Hi,
>
> I'm looking for any tool or a way I could specify a CIDR and the prefixes
> that are being used within this CIDR and the tool show me all free
> supernets.
> <snip>


I've used subnetsmngr for this in the past. Proper usage of it thru the UI forces you to fully allocate (as compared to 
sparse allocating) your subnets, basically the same way subetting is taught in base level networking certifications. 
This makes finding the un-used subnets very easy.
http://sourceforge.net/p/subnetsmngr/wiki/Home/ <http://sourceforge.net/p/subnetsmngr/wiki/Home/>

NIPAP allows you to do the same as well, but will let subnets be sparse allocated, so you won't necessarily have 
pre-created them waiting to be used later on. 
http://spritelink.github.io/NIPAP/ <http://spritelink.github.io/NIPAP/>
NIPAP also has a nice CLI interface.

Both are also open source, full v4/v6.

Theo