THG3000 Router. Oddity with MAC Filtering. Device still shows up.

[bordonbert]

Hi guys. Sorry in advance if this becomes a convoluted issue and I may not be too clear with details, some aspects of it are really foxing me.

I'm using a Vodafone supplied THG3000 router with Guest WiFi disabled.  I have a wireless device showing up on my network under Overview which I do not recognise.  It is listed as a Galaxy Note 3 mobile phone which is not a model any of my household have.

I have a small TP-Link Nano WiFi extender in action as an access point in another part of the house and I suspect the device connects through that rather than the main WiFi in the THG3000.  I think that may cause a slight complication as I suspect those devices may then show up as LAN connected in the main router.

I have identified the rogue device in the main router reporting.  It is listed under Network not under WiFi.  I am assuming that, as it connects wirelessly via the Nano I have enabled MAC Filtering on my WiFi, entered it as Deny and blocked it.  It took a restart of the router and it does not seem to have been given an IP address.  However, it is still showing in the Network list, not under WiFi, just as it was but now it is greyed out.  I don't like how that device is still showing up even though it seems to have been denied entry as it should.  What are the reasons for that?  If it is not connected and a part of the network why is it listed at all?

Incidentally, I use Eset Smart Security Suite on all my network devices.  The rogue device is currently showing in Eset Network Inspector as last seen 35mins ago.

[Cynric · Accepted solution]

@bordonbert If the odd device is only showing it's MAC address and no IP address associated with it then it is not a concern. The device has at one point been in range and "looked" at your router. All devices do this to see if the router is one that it has access rights to connect to it. It will disappear from your router in time. You may also be able to see it from Windows File Explorer if you select the Network icon, but again it will have no IP address and will not be selectable. On odd occasions I can see my neighbour's television like this.

[bordonbert]

Thanks for the advice Cynric.  The most worrying aspect has to be that this device was logged in to my network with an IP address which could be pinged before I set up MAC filtering to exclude it.  There was no way to simply kick it off the network, a router reboot just meant it immediately appeared and logged in again when the router came up.  I had to set up the MAC exclusion and reboot the router to prevent it from logging in.

My passwords are all randomised 20+ characters with caps, numbers and symbols generated by Eset's Password Manager feature.  How it got an IP address I have no idea.  Just as you say, now it has no IP address it appears to have vanished completely from Eset's Network Investigator panel.  It is still listed in the Router Management Suite Network list but, as I said in the first post, it is greyed out and inaccessible to clicking for details.  I think it has been sorted out now .

If it reappears again I'll be back to report it.