B450-F Gaming - Network speed capped on 100 Mbps

[CRUISER]

My PC config:
Ryzen 5 3600
2 x 8 GB G.Skill Ripjaws
EVGA RTX 2080
Corsair RM850x
Windows 10

It had been working well for more than 12 months then suddenly I noticed the internet speed dropped from 600 Mbps to less than 100 Mbps per https://www.speedtest.net/. The PC is connected to the router by an ethernet cable. These are the troubleshooting steps I've followed:

1 - Restarted my own router and modem - I have Comcast internet 600 Mbps DOWN / 20 Mbps UP
2 - Changed the ethernet cable connection to other ethernet connector on the router
3 - Changed the router with other one
4 - Changed the ethernet cable
5 - Noticed the Ethernet Status on Windows 10 was on 100 Mbps instead of 1000 Mbps
6 - Removed and reinstalled the network driver, and same issue, no 1000 Mbps.
7 - Connected 2 other distinct computers running Windows on that ethernet cable and they presented 1000 Mbps properly
8 - Ran a Linux distribution on a flash drive and the motherboard continued giving me 100 Mbps instead of 1000 Mbps
9 - Upgraded the Bios to the latest version 4801, and the network status continued showing 100 Mbps instead of 1000 Mbps
10 - Reinstalled Windows 10 on a spare SSD drive and the network status continued showing 100 Mbps instead of 1000 Mbps

This troubleshooting showed me there's an issue with the network hardware on the motherboard that doesn't allow a 1000 Mbps connection.

I'm gonna contact ASUS support to see the procedure to return the motherboard for repair.

Any other thoughts, please let me know. Thanks in advance.

[Enrrir]

I know it has been a long time man, but have had any help woth that? I`m having this exactly same issue

[chinchillas33]

I've encountered the same problem. MSI Tomohawk B450 's ethernet port supports 1GB speed but mine was capped at 100Mbps.

I just changed my old ethernet cable to cat6, now it shows speed of 1000Mbps ethernet port.

You need to change ethernet port speed on windows if it doesn't automatically do it for you.

[Jiaszzz_ROG]

Hello, @chinchillas33 

As we are the ASUS ROG official forum, based on the specifications you have provided, we would recommend that you contact the customer support of the relevant manufacturer's for further assistance.

Thank you.