@Mschiff 

I would look at firewall, QoS, VPN, and DNS as possible causes. 
 

Also when you test, is the wifi on or off and is there other devices attached to the router?

ArcherC8 wrote

  @Mschiff 

 

I would look at firewall, QoS, VPN, and DNS as possible causes. 
 

Also when you test, is the wifi on or off and is there other devices attached to the router?

 

 

Thank you very much for your reply and suggestions.

I don't think it could be any of those things, because when I connect to the 2.5Gb port, everything is symmetrically correct. I get close to 2.5 Mbps on my computer up and down. If I connect to the 10Gb combo port, I get 3Gb down and 500Mb up consistently. If it was DNS, wouldn't it effect the 2.5Gb  port as well?

I did turn off QoS, and my software VPN (Malwarebytes) was off. 

Also, the 10Gb port is unreliable. Periodically, it just cuts out. Never any problems with the 2.5 Gb port.

I tried it with WiFi off and on. No difference. Nothing else was connected when I tested, but it did not make any difference if I connected my 1Gb  switch to a 1Gb port.

  @Mschiff Have you tried different drivers for the 10G controller make and model will help to dig deeper, some don't do auto negotiate so have you tried 10G full duplex on adapter properties-advanced-speed and duplex, some ISP's put the speed test server on the last hop before route hits the actual internet to save on bandwidth along with a google server to keep queries off the backbone.  

@Sammael1069 I used the driver that was provided with the adapter. It is a tp-link 10 Gigabit PCIe TX401. I figured that since it is the same brand as the router, that it would be compatible. Yes, I went into the adapter properties and set it to 10G, but that made no difference.

I spent hours searching the internet for suggestions and tried quite a few with no change.

I also called the support line for Wow! and they were no help.