@terziyski It should be set on auto-negotiation. Both sides of the cable should have the same setting if you try changing it. I would try a different cable first, and check if it plugs in properly....

I didn't tested this specific router, but expect same 1 Gibps or close. Assuming the laptop has 2x2 Wi-Fi 6 (802.11ax) 160MHz bandwidth capable card and it isn't some crowded multi-family building...

@Zigwilly You can connect already working WAN cable to a LAN port (leaving other cable end where it is) and check in router control panel like http://192.168.0.1 > Network Map > Your Router Name >...

@MMMcQ You should figure out if the router negotiates the 2.5G speed at ethernet level at all. This is lower level before any tcp/ip or internet. I had wrote above where to look. If it doesn't, or...

Router does NAT, a switch doesn't. So you will not get more than 1 device on internet without NAT as ISP provides only 1 IP address. At this point I lost track what results are you getting connecting...

I'm not sure we are on the same page regarding speed and half/full duplex. There are few options: 2.5G full duplex. 2.5G half duplex. 1G full duplex. 1G half duplex. etc. Half duplex is basically...