Gig Speeds on RT-AX88U

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Louis James

Occasional Visitor
Good Morning:

I have the RT-AX88U with Merlin 386.3_2 sitting behind a Motorola MB8600 (DOCSIS 3.1). My ISP (xFinity) claims I have 1.3 Gb speeds Down / 35 Mb Up. However when I run a Speedtest at the router (Adaptive QoS / Internet Speed) I get 601 Mb Down / 42 Mb Up).

I have done the following:

  • Shut down the entire network except the router and one computer (Wired).
  • Changed Jumbo Frame to Enable (Lan/Switch Control)
  • Changed the same setting on the computer NIC and also turned of Auto Negotiate to 1.0 Gb (Instead of Auto)
The ISP "claims" It's my equipment (router/computer) and that it "can't handle the speeds." However, if I try the same test WITHOUT the Asus router (ISP--->Modem-->Computer), I get similar speeds. I have tried two (2) other modems from them (XB7) and get similar results. The XB7 is in bridged mode. The Motorola is a straight up modem.

Is there any additional settings in the RT-AX88U that I might need to adjust? Syslog.txt is attached (2021-09-16-syslog.txt).

Thank you for any thoughts/assistance/ideas you might have.

Regards:

Louis
 

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  • 2021-09-16-syslog.txt
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ColinTaylor

Part of the Furniture
My ISP (xFinity) claims I have 1.3 Gb speeds Down / 35 Mb Up. However when I run a Speedtest at the router (Adaptive QoS / Internet Speed) I get 601 Mb Down / 42 Mb Up).
To achieve >1Gb both the router and the MB8600 must be configured for link aggregation (using two Ethernet cables). If you're only using a single cable make sure link aggregation is disabled on the modem otherwise your speed will be halved.
[I'm reading conflicting information on the internet about the MB8600. Some sites say it only has a single Ethernet port while others say it has four.]

I notice that you're also running a VPN client on your router. Turn that off when testing your speeds.
 
Last edited:

Louis James

Occasional Visitor
To achieve >1Gb both the router and the MB8600 must be configured for link aggregation (using two Ethernet cables). If you're only using a single cable make sure link aggregation is disabled on the modem otherwise your speed will be halved.
Wow Colin! Thank you so much. This is fascinating. A few notes:

  • The MB8600 only has one port. However, the xFinity XB7 has four (4) ports. So your suggestion can be accomplished.
  • Enable WAN Aggregation is set to NO. When I switch over the XB7, I will try that.
  • VPN Client: I will also turn that off to test
Colin, thank you so much. I will report back my findings.

Louis
 

ColinTaylor

Part of the Furniture
If your MB8600 only has one port then it's not possible for you to be using link aggregation (which requires at least two ports). So my theory about that being the cause of your problem won't be that case.
 

pvanryn

New Around Here
Even without link aggregation, you should be doing much better that 601 down. I have a RT-AC86U and I connect to Xfinity through the XB7 in bridge mode and I average about 940 down and 40 - 45 up.
 

Louis James

Occasional Visitor
If your MB8600 only has one port then it's not possible for you to be using link aggregation (which requires at least two ports). So my theory about that being the cause of your problem won't be that case.

I just had a long conversation with Motorola Tech Support and found out a few things:

  • While the MB8600 is "theoretically" a Gig device, the best that it can do is 800 - 900 Mbps (in a perfect world).
  • I reset the MB8600 and got to 700 Mbps.
  • Cat 6 is required. I have Cat 5e (running to Best Buy now!)
If I truly want 1.3 Gb, I would need to upgrade to the MB8611 (capable to 2.5 Gb) and still need the Cat 6. It only has ONE port so link aggregation is out. But if it does hit the speeds we are ok.

On the way to pick up the modem.
 

ColinTaylor

Part of the Furniture
If I truly want 1.3 Gb, I would need to upgrade to the MB8611 (capable to 2.5 Gb) and still need the Cat 6. It only has ONE port so link aggregation is out. But if it does hit the speeds we are ok.
This is a strange comment. AFAIK your router doesn't have a 2.5GbE WAN port. Therefore when you plug it into the MB8611 (which has a single 2.5 GbE port) the link will still only be 1Gb. Therefore you'll only get ~940 Mbps throughput.
 

Louis James

Occasional Visitor
This is a strange comment. AFAIK your router doesn't have a 2.5GbE WAN port. Therefore when you plug it into the MB8611 (which has a single 2.5 GbE port) the link will still only be 1Gb. Therefore you'll only get ~940 Mbps throughput.

Well I have some "interesting" news. I'm not saying that it correct or setup correctly, just interesting. First, I turned off the entire network except for the Cable Modem, the Router and one computer. The results::

  • I spoke with Motorola on the MB8611 and the tech gave me some "Interesting" news. If xFinity loaded the wrong "BEND" file (apparently a file that determines the speed I'm supposed to get, that could be the cause of the problem. I called xFinity and was able to reach a tech that was willing to help. His comments were that "something is screwy" with my profile. After a good while, (I think he was fixing things), we got better speeds - in the 700 - 800 Mbps range.

  • I then went and turned off Wi-Fi on the Asus router (Wireless/Professional/Enable Radio) and turned off both 2.4 Ghz and 5.0 Ghz. That improved the speed a bit more.

  • I then turned on QoS (Adaptive QoS/Qos) and turned off "Enable Qos"

  • With Both Qos Turned off and WiFi Turned Off, I'm getting around 943 Mbps

  • With QoS Turned On and Wifi Turned Off, I'm getting around 764 Mbps

  • With Qos Turned Off and WiFi Turned On, I'm getting around 941 Mbps.
All these tests at the router Speed Test. Not at the computer. I have to wonder is QoS is part of the problem? You would think that QoS would improve speeds. Of course, how QoS is set up can be a factor. But to significantly drop from 941 to 650 to 764 seems to point to QoS. I've turned on WiFi as that seems NOT to have an effect. Although I have a Mesh (Netgear Orbi Pro) hanging off the router.

While this is not the forum, I did suggest to Motorola that they should give us an ability to see how an ISP has setup our Modem. I suspect that the primary problem is that xFinity didn't send the right file. Maybe. Who knows.

Colin and all, thank you for all your help. I am open to making additional changes to the router if you have any. Thank you again.

Regards:

Louis
 

ColinTaylor

Part of the Furniture
Thanks for the update @Louis James. As noted above ~940 Mbps is exactly what you would expect for a 1Gb connection.

There have been reports of QoS limiting speeds similarly on other models of router. You may be able to avoid that depending on what type of QoS you're using and how it's configured. It's also worth verifying what the speed is from an Ethernet connected PC rather than just the built-in test.

But the general consensus in these forums is that with very fast connections like you have there's rarely any need to enable QoS so most people leave it disabled.
 

maxbraketorque

Very Senior Member
One comment I'll make is that I've found that browser-based speed tests can't measure more than about 750 mbps. I had to use the Ookla app on a ethernet'ed computer to see 940 mbps with my xfinity 1 gbps connection. Also, I agree that while Cat 5e is supposed to be capable of 1 gbps, I see a clear improvement with Cat 6.
 

Wisiwyg

Senior Member
Thanks for the update @Louis James. As noted above ~940 Mbps is exactly what you would expect for a 1Gb connection.
Can confirm, without LinkAgg between modem and AX88U the *best* I've seen is ~920-940 with Comcast 1.3gb line - with everything turned off, like Skynet, AIProtect, etc.. With link agg btwn AX88U and modem with 2x CAT6 cables the best I can get is 1.2gb, still not full 1.3gb. Note I also have link agg from the AX88U LAN ports to a managed switch, and from there all the home network hardlines connect. But not complainin', that 1.2gb is sweet!
 

ColinTaylor

Part of the Furniture
Also, I agree that while Cat 5e is supposed to be capable of 1 gbps, I see a clear improvement with Cat 6.
Cat 5e is easily capable of 1Gbps, assuming the cable is up to spec. That's what it was designed for. We're only talking about a patch cable between the modem and the router so I don't know what kind of improvement you're thinking about. 1Gb is 1Gb.
 

Treadler

Very Senior Member
Well I have some "interesting" news. I'm not saying that it correct or setup correctly, just interesting. First, I turned off the entire network except for the Cable Modem, the Router and one computer. The results::

  • I spoke with Motorola on the MB8611 and the tech gave me some "Interesting" news. If xFinity loaded the wrong "BEND" file (apparently a file that determines the speed I'm supposed to get, that could be the cause of the problem. I called xFinity and was able to reach a tech that was willing to help. His comments were that "something is screwy" with my profile. After a good while, (I think he was fixing things), we got better speeds - in the 700 - 800 Mbps range.

  • I then went and turned off Wi-Fi on the Asus router (Wireless/Professional/Enable Radio) and turned off both 2.4 Ghz and 5.0 Ghz. That improved the speed a bit more.

  • I then turned on QoS (Adaptive QoS/Qos) and turned off "Enable Qos"

  • With Both Qos Turned off and WiFi Turned Off, I'm getting around 943 Mbps

  • With QoS Turned On and Wifi Turned Off, I'm getting around 764 Mbps

  • With Qos Turned Off and WiFi Turned On, I'm getting around 941 Mbps.
All these tests at the router Speed Test. Not at the computer. I have to wonder is QoS is part of the problem? You would think that QoS would improve speeds. Of course, how QoS is set up can be a factor. But to significantly drop from 941 to 650 to 764 seems to point to QoS. I've turned on WiFi as that seems NOT to have an effect. Although I have a Mesh (Netgear Orbi Pro) hanging off the router.

While this is not the forum, I did suggest to Motorola that they should give us an ability to see how an ISP has setup our Modem. I suspect that the primary problem is that xFinity didn't send the right file. Maybe. Who knows.

Colin and all, thank you for all your help. I am open to making additional changes to the router if you have any. Thank you again.

Regards:

Louis
I have previously had a 1000/50 connection on my router.
Any QOS configured reduced my max throughput to what you were seeing. No QOS is the way on gig plans IMHO.;)
 

maxbraketorque

Very Senior Member
Cat 5e is easily capable of 1Gbps, assuming the cable is up to spec. That's what it was designed for. We're only talking about a patch cable between the modem and the router so I don't know what kind of improvement you're thinking about. 1Gb is 1Gb.

The best I can say is that for the LAN connection between my NAS and my ethernet'ed computer, the speeds got incrementally closer to the 1 gbps theoretical max when I switched from Cat 5e and Cat 6. My recollection is something like a 10% improvement in speed. Perhaps the Cat 5e patch cords I had were not up to Cat 5e spec. These days, I pay more to the cable design than I do the claimed spec.
 

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