how to -Ethernet- Mac address whitelist asus built in firmware

I have an rt-ac 3100. I need a deterrent to non-authorized devices using both wifi and ethernet. I know there is a wifi mac filter whitelist which would be perfect, except it only applies to wifi. I need something that also applies to ethernet. Basically, I'd like to be able to go in and say allow this mac address and it would allow the device to connect to the network/internet. all unknown mac addresses would not be allowed. Any ideas?

I have one, but would like a better one...

how to -Ethernet- Mac address whitelist asus built in firmware