Ok great, so yeah, as suspected, there were VLAN settings being applied to the ethernet ports. This does beg the question though, as to whether you enabled that at some point yourself, or, was the 'Reset' attempt unsuccessful!
On the 'LAN >> VLAN Configuration' page, you could simply just de-tick the 'Enable' option and the router will return to its generic LAN mode, whereas now, you have the VLANs enabled. Not a big deal, in fact, it means you're ready to start segregating your network if you so desire; which in my opinion will be rolled-out by ISPs (via their modem/routers) at some point in the not-too-distant future, as there are too many vulnerable IOT devices in people's domestic dwellings and even in small business environments.
VLANs allow you to steer packets around your network as they pass through switches and routers, effectively giving you isolated networks but all via the same physical cabling environment, ie, you don't need to run two lots of cables and switches for each separate network.
The packets get tagged with a marker when entering a VLAN capable network device and that marker is used to track the packet within the device making sure it leaves out of the correctly designated port or ports. Additionally, packets can be given universally recognised markers, called 'Tag IDs', which allow many differing ID tagged packets to be sent via a single port, or many ports, to other network devices that can also understand the Tag ID's and forward them on to their designated port, or ports, until the packet eventually reaches its intended device/node.
Tag IDs are best thought of as being used BETWEEN devices, rather than imagining them internally within a device, as devices will strip and add Tag IDs when and where they are required, kind of like a postal service sorting office, where a sorting office would have its own internal processing system yet the packages still leave the sorting office with their designated destination clearly labelled; and lets say “untagged” packet are kind of like a parcel that arrives at your door with the address label removed - because it is no longer needed; the package has reached its intended recipient.
Tagged packets have a marker(ID) added to them when leaving a device
Untagged packets have the marker removed or no marker added to them when leaving a device and are just plain old packets; because the device at the end doesn’t need to know, or doesn’t know how to process, the Tag ID.
On a quick search through your model's manual, I couldn't find an option to disable the ethernet ports, so that was a bum-steer by me, apologies; odd though, that it doesn't have that capability, of disabling unused ethernet ports.
