how to hide/fake the LAN IP on Browser

hey,

how can i fake my LAN IP?
i use proxies for chrome and firefox.
when i check my ip on whatsmyip.com the real ip works yes, but whats about the lan ip?
when "whatsmyip.com" can track/read the lan ip, can every site track me with that??
the site also can read my LAN Ip (scroll to the bottom of the site to "your COMPUTER")

regards

Disable WebRTC. The browsers are the ones 'leaking' the internal IP.

Read more here: https://www.google.com/amp/s/www.privacyend.com/disable-webrtc-in-various-browsers/amp/

Some advanced websites track you through mac address even. You can hide your internet IP through a OpenVPN.