Question re IPs-to-CIDR conversion program

Duane Hill d.hill at
Fri Aug 1 15:58:20 UTC 2008

On Fri, 1 Aug 2008, Mark Wilson wrote:

> I'm trying to write a program that will take 2 IPs and return an appropriate CIDR which contains both.
> I found this file: listed under ~eivind on FreeBSD, which sounds like it might be a good model.
> Unfortunately, I can't download the file (get "Forbidden") page, nor locate user "eivind" on the FreeBSD Homepages page to ask him/her about it.
> (It's dated 2001, in case that helps; apparently eivind is long gone...)
> 1. Can anyone get me a copy of this program? Or...
> 2. Put me in touch with its author so I can ask about it?? Or...
> 3. Point me to another program which does what I need?
> Thanks. I'm very new to all this; I was able to cobble together a CIDR-to-IPs calculator in JavaScript, but going this other direction seems much harder, and far more confusing.

If you know anything about Perl, you can use the port:


to convert back-and-forth. For documentation, I referred to:


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