This might help.
Last week I installed an Asus Prime Z490-A that included an Intel i225-V Ethernet port. The Windows Device manager indicated the Ethernet port was properly installed but it appeared dead and Windows saw no connection. Neither light on the RJ-45 connector was lit. The Windows trouble shooter stated there was no Ethernet cable plugged in or the cable was bad. I verified the Ethernet cable, direct from an AT&T RG, worked properly by plugging it into my laptop. However, when plugged into the Z490-A, neither of the two lights in the RJ-45 connector would light. I called Asus and they had me install three different drivers but none fixed the problem. Asus then said the board was defective and a new board was shipped. The port on the new board also did not work. After hours of troubleshooting, something, I do not know what, made me think to simply insert a powered switch between the Ethernet cable and the Z490-A. The socket instantly came alive with both lights lit and Windows immediately connected to the internet.
The AT&T RG is in another room and the cat5e cable from it is a home run from one of the four yellow RJ-45 sockets on the back of the RG to a RJ-45 socket in the wall behind my desk. A six foot jumper then went from the socket in the wall to my computer. Now the jumper goes to a four port 1000M switch and another jumper goes from the switch to the computer. The switch has nothing else connected to it. Although my laptop, and two other computers have used this socket directly without any issue, the Asus Prime Z490-A with the Intel i225-V Ethernet port would not connect to it.
I am going to leave well enough alone now as it works but I am thinking one of the cat5e cables between the AT&T RG and the computer should be or should not be a crossover cable. My guess is most Ethernet devices are insensitive to this but the Intel i225-V might be. The 1000M switch makes any crossovers behind it (toward the AT&T RG) invisible to the i225-V and only a single commercial cable that came with some device I bought sometime in the past is now between the computer and the switch.
Last edited by RhoXS; 07-09-2020 at 01:33 PM.