It looks to me that your router has multiple components within it, and this is not uncommon. As CaveDweller said, there are two components to the router. I would like to add that there may be more than that, depending on the device functions. In this case it looks like you have a wireless function linking to a switch for all wireless devices (BT could mean Bluetooth, but I doubt it in this case). Then you also have a hardline component, which is essentially another switch. These two separate switches must talk to each other in order for traffic to move between them, so it looks like they were hard wired together with a HUB in the middle. So now the wireless traffic can touch the hard line traffic, which is where the inbound/outbound network traffic hits your ISP from. Personally I feel this is a bit of a mess, but it may have been done to increase the number of collision domains, since wireless tends to have a lot of those. Or maybe it was to reduce a specific failure in their device that they identified. I could guess at the reasoning all day and never be correct, but the network diagram shows that either you have multiple physical devices connected this way (but you said that you did not) or that this is the internal logical structure.
Keep in mind that I said LOGICAL structure....this is how the network layer of the OSI model sees your network. This does not mean that each is a separate device, rather a separate function.
Now, if you see another computer appear near your other wireless computer....then you may have a problem. Or is you see an unknown wire connecting to your router....but this is extremely unlikely. Right?
-- Windows 7 Ultimate on custom built system, Windows 10 on under powered laptop. Sophos UTM 9, Ubuntu Server and Windows Server 2008 R2. HyperV Virtualization --
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