Had Xfinity come out and confirm I had Gig speed to my SB8200 cable modem. Same problem as described here, only getting about 700Mb from the AX11000. I did the speed update settings but no luck as of yet. I'll keep trying. 
Thanks though for the recommendation Bill. 

@DMas21 -

Well the SB8200 only has 1 Gbps Ethernet ports so you can't get full speed from it. You need a Cable Modem with a 2.5Gbps (or faster) Ethernet port, like the CM2000.

 
If you connect your laptop directly to the SB8200 without going through the AX11000 what speed do you get using speedtest.net (you will need to power cycle the SB8200 to get it to recognize your laptop's MAC address)? That or greater would be the speed limit you should set in the QoS settings on the AX11000. We just set our QoS limits to2500 Mbps and it works fine. 

You should be able to achieve speeds of over 900 Mbps using 1 Gbps Ethernet, that's the maximum you can expect due to Ethernet overhead.

Note - Speedtest on the AX11000 still won't report better results, so ignore it. Use Speedtest on a computer or laptop. 

Regards,

Bill

@BFinkelstein 

I think 2.5GbE port can't delivery full speed.

I've connected 2Gbps Internet to 2.5G port and do speed test. I can delivery only 1 Gbps maximum.

Seem the 2.5 port can't work right now

@MAXiMUSMX-TH How did you determine that? 

Since Speedtest on the AX11000 isn't working right and it only has 1Gbps Ethernet LAN Ports, the only way to measure would be measure it's output is if you got really close to the router with a device that supports really fast WiFi, connect via 5Ghz, verify that your WiFi connection is much faster than the 2 Gbps based connection, and run a Speedtest that way. Even then WiFi has so much overhead that you won't get full speed.

For example, going through the AX11000 on an Ethernet connected PC on my 1.4 Gbps Internet connection (as tested with on a PC connected directly to my cable modem through at 2.5 Gbps adapter) I get speeds in the 900 Mbps range (as expected on a 1 Gbps connection).

Standing right next to the router my WiFi 6 connected Samsung Galaxy S21 Ultra establishes a 1.2 Gbps WiFi connection to the router (as verified in the details about the connection on the phone). However Speedtest on the phone only reports 381 Mbps. 

IMHO, you'll never see speeds faster than 1Gbps on any individual device unless said device is connected to Ethernet, has a 2.5Gbps Ethernet adapter, and is connected through LAN Ethernet ports faster than 1 Gbps and have everything connected at 2.5Gbps or better. 

@BFinkelstein I'm having the exact same behavior but this didn't resolve it. Everything is still speedtesting at about 600 down and 800-900 up. I was so excited to have found a solution too, but it seems like I'm nearing the point of returning the unit.

@BFinkelstein 

Went and looked at this setting on my AX11000, best I could tell was that the QOS, reverted to the slowest tested speed.  My original speed test showed around 997Mbs fro a wired desktop, then I ran the same tests from around my house using laptops and the speed was slower but still good for WiFi, what I then noticed is things were slower. I made the change to a manual setting for my speed and the tests then got faster. 

I will run some more tests but it seems to be an adaptive QOS that slows things to the slowest device that a speed test was ran from. 

If I use the routers speed test I get 53/18, if I go to speedtest.net I get 938/18.

Why incorporate speedtest.net if you are going to do it so badly?

Xfinity: 928/18

Speakeasy: 943/18

DSL Reports: 859/19

AX11000: 69/18 <-- WTF?

I ran that after I ran the 4 tests I mentioned above at other sites. 

Seriously, why include it and mislead customers?

I want to turn QoS off until I know it works, how?