SysInfo: LAN IP address changes when logged into a VPN

[axolotl_soft]

While this might be more of a general networking question than one strictly related to Rainmeter, it's one of those ones that Google can't answer for me, and it's burning me up inside:

I've made a skin. It uses, among other things, the SysInfo plugin to pull and display the LAN IP address.

I also use a VPN. I've noticed that my LAN address changes when I log into the VPN, but that I can pull what I'll call my 'true' LAN IP (the one produced by ipconfig in a cmd prompt) address by changing SysInfoData from 1 to 2.

Why on earth?! Is this behavior internal to the machine or just native to the plugin?

(I've read the SysInfo documentation, but don't have any understanding of 'installed' vs. 'active' IP addresses.)