How to assign internal addresses to regions of the Russian Federation (GeoIP + Piwik)?

Question

Geolocation

There is a site (it has Piwik with GeoIP (PECL) location enabled), which is used both on the local network and by users from the Internet. If there are no problems with the latter, then how to determine the region from which the user accesses from the local network?
I have a strict correspondence between IP and the region of the Russian Federation, the whole problem is how to register these pairs in the GeoIP database.
They have something like that on their website, but everything is not intelligible there. :(