unknown ethernet device on router

[oldnich]

have had router problems for a few days, router has been rebooted several times. 

I just logged onto the router to chek devices and i see an unknown device listed, as an oethernet connection - I don't have anything connected via ethernet so what is it ?

I see other posts suggesting unknown devices may be orphans unexpired leases, but this doesnt have a ip address, and the connection type is listed as other - not wifi, which all my devices are 

Obvs I've looked at the router and there are no ethernet cables connected, my only cables are the power cable and the connection cable 

[Gareth_L]

Hello oldnich.

Thankyou for bring the unknown device to our attention.

I have checked the mac address for the device and it not showing anything at all.

Would you like me to take a further look at this for you?

If you don't mind, I will need to send you a private message to pass security. 
If you can check the Logo top right of your screen that would be great. 
Regards     
Gareth_L
 

[Tudor]

Have you got any mobiles with "Privte WiFi addresses" set in them? This can cause this type of behaviour.