@BFinkelstein 

SOLVED!????

No, NOT SOLVED.

I JUST GOT THIS and this is exactly why I left Cisco/Linksys because of this same type of "Solved" issues that get swept under the rug...

My Uploads are reporting U/300mbps when I'm getting 940+ U/ from my cisco/linksys and I have done EVERY recommended step!!

This is going back to Costco and I'm leaving reviews on there, amazon, youtube and all the forums I know.

I can't believe some people have dealt with this for over a year!

wow.

I think I might have the same problem with my AX6000. I have an Internet only plan with Xfinity. I originally had 300 mbps plan but over the past 2 years was upgraded to 600 mbps (paid for this) then updated to 800 mbps and then 900 mbps for free. When I was updated to 600 mbps and ran SpeedTest I would get 600+ mbps all the time at the Ethernet ports. In April 2020 I decided to get my own NetGear Cable Modem and Router to save money and have a stronger WiFi signal. I got a NetGear 1150 which was advertised as DOCSIS 3.1 up to 800 mbps at that time. I got it setup and activated. However, ever since being upgraded for free to 800 mbps and then 900 mbps I cannot reach these speeds. I’ve had numerous calls to Xfinity Advanced Technical Support. They would send a command to the modem and it would jump up to the speed I’m promised. However, within 15 minutes, it would drop back down again to 600+ mbps at the Ethernet ports. I had a Xfinity technician come to my home last week to check out my lines. He replaced all of the cable connectors in the house and gave me a new cable between the wall outlet and the cable modem. I had prior to his visit bought new CAT6 cables to go from my modem to the router and from the router to my iBuyPower Gaming PC. Before he left, his device showed the signal at 900+ mbps. I tried to login to my modem but it wouldn’t take my changed password or the default. I disconnected it from everything and turned the power back on and pushed in the Reset button for 10 seconds to completely reset it. I then connected it to the cable line and after about 15 minutes it was working properly. I connected it to my Router, turned it back on, logged into my PC and ran Speedtest. I was finally at 900+ mbps. I checked 15 minutes later, and it had dropped back down to 600+ mbps. I checked the Modem event log for several days and it was empty, no new events. I have found that if I go to the Xfinity Support Site and click on Restart Modem, wait for it to complete, turn off the Modem, unplug the power cord for 30 seconds, plug it back in, restart the modem and when ready restart my TP-Link Archer AX6000 router and run a Speedtest that I’m at 900+ mbps again. However, when I check 15 minutes later, its dropped right back down to 600+ mbps. So, I decided to get a new NetGear CM1100 Modem at Costco, rated up to 2GB mbps. I came home, disconnected the old modem, plugged in the new one, activated it with Xfinity and connected it to my TP-Link Archer AX6000 router and started it. I ran a Speedtest that I’m at 900+ mbps again. However, when I check 15 minutes later, it’s dropped right back down to 600+ mbps. Can I solve this as suggested by going into "Advanced" -> "HomeCare" -> "QoS" and manually edit the "Total Bandwidth" to my  actual Internet service values?

*** Problem Solved! ***

I changed the QOS value from 600 to 980, rebooted the router and now I'm getting 900+ mbps all the time! Thank goodness I found this thread!

@11bravoxray - Where in my AX6000 can I change the duplexing from Auto to my higher service? I searched the entire PDF manual and didn't find the word "duplex" anywhere.

Just wanted to chime in about my experience with a similar issue, but using the AX4400. Some background: I have 1 Gbps fiber internet service. After pruchasing the AX4400 I noticed my internet speeds via ethernet were a little slower than expected at about 300-700 down/up depending on time of day. To check this and verify what I should be able to pull from my ISP, I was able to get 850-900 down/up using a much older ASUS RT-N66U router.

In my TP Link AX4400 I had QoS turned on (via the tether app) with 1000.0 Mbps down/up set as the speed. Interestingly, with QoS turned on I also saw very large bufferbloat on the order of 90-120 ms. Again, this is all connected using 1 Gbps full duplex ethernet cat5e cables, and almost no bufferbloat when using the RT-N66U.

After reading this thread, and seeing that others wanted to turn off QoS but were unable to do so for their specific router, imagine my surprise when I realized I could simply turn off QoS from the tether app. So, after I turned off QoS, I retested the AX4400, and I was able to get full speeds from my ISP. In addition, bufferbloat went away, almost entirely, at +1-2 ms for loaded latency. On wifi I do see some bufferbloat, but it's 60-90 ms less than before when QoS was enabled.

@dav_4400 Unfortunately for the AX11000 the Tether App doesn't give you the option to turn off QOS. I wish it did!

@BFinkelstein I had, quite literally, the exact same issue with my router (AX4400 v1.6) after a firmware update. I was suddenly getting half the speed from my fiber connection with no idea what had happened.

Went into HomeShield and found QoS had been turned back on without my knowledge. Turned it off and all was back to normal.

  @BFinkelstein 

Very interesting thread here.  I'm currently running a Netgear Nighthawk X6 AC3200 router with FIOS GB service.  Cat 6 direct from the ONT (FIOS box) to my desktop tests out at 1GB service (Verizon speedtest).  As soon as I run thru the Nighthawk, the Verizon speedtest shows 250mbps D/L.  The Netgear forums have a very similar thread to the one on this site.  I was looking for a replacement router this evening and ran across the TP-Link AX 11000.  Now this thread makes me wonder if a GB router exists.  My next stop is Asus and their forum. 

  @Zman44 TP-Link The AX 11000 works great at 1 Gbps. You only have to override the erroneous QOC settings if you use the internal Speedtest.

I don't know about your setup, but you might look into your routers control panel and make sure you're cables are actually good and you're not shifting down to 100 Mbps. I've had other routers not like a CAT 6 or Cat 7 cable and do that. The TP-Link router works fine over the same cables.