What it does
Router
UPnP can let devices and apps on the local network request port mappings automatically. That can make games, calls or other services work without manual setup. It also means an untrusted local app may request exposure you did not intend. It is separate from the router's remote-administration setting.
Example
A console requests a mapping for online play. Later, you see an unfamiliar mapping for a computer you do not recognize. Inspect the device and app before deleting or keeping the rule. ASUS
advises leaving UPnP disabled if normal use continues without it; router menus and needs differ.
A measured choice
Review existing mappings, disable UPnP if you do not rely on it, then test the apps you use. Re-enable only with a reason and keep the local devices trustworthy. Turning it off does not automatically remove manually configured port-forwarding rules; inspect those separately. An unexpected mapping is also a reason to inspect the requesting device, not only the router toggle.
