CIDR Utilization

Theodore Baschak theodore at
Sat Oct 31 02:50:54 UTC 2015

> On Oct 30, 2015, at 7:51 PM, John Steve Nash <john.steve.nash at> 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. <>

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. <>
NIPAP also has a nice CLI interface.

Both are also open source, full v4/v6.


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