creating a local geoip db (no replies)

We are on piwik 2.9.1.

I apologize if this has been asked before, but so far I have not found it.

I was thinking of setting up a local geo ip db. In other words, we have many ip with local ips (10.*) ones internally
and I wanted to know how to find the format of the db and what the process is to set it up for processing by PIWIK.
I see that PIWIK has Organization Database on the Geolocation page. I also would not enter every ip, just the ranges
if possible mapped to the location related to the range.

Thanks,
Douglas