Whatever the case it’s better to stay on the safe side.
The address you need should be next to Default Gateway under your Local Area Connection.
Once inside your router’s administrative console look for a section related to connected devices or wireless status.

Check that list against your gear to find any intruders.
The MAC address will be shown as the physical address.
It won’t stop the most determined intruder but it will slow him down.
Must see:The best routersreviewed and rated.