[SOLVED] ASUS RT-AC66U capped at 100mbps over 5g 802.11ac

JustSomeNumbers

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Jan 22, 2014
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So I've got the aforementioned router, and I've seen it get ~200mbps over the wifi on this exact same setup, but after doing a factory reset and installing Merlin onto it, I can't get wifi above 100mbps, like it's limited somehow. Clearing NVRAM manually over telnet hasn't fixed the issue, neither has going back to the original ASUS firmware. I've got no idea what the problem could be and I'd really appreciate some help. Let me know if there's any more information that's needed, I'll happily provide it.

Edit: I should add that when plugging my laptop directly into the cable modem I get full speed of ~200mbps down, but through my router every device, wired and wireless, caps out at 100mbps over 5g/wired and 50mbps over 2.4g.
 
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JustSomeNumbers

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Jan 22, 2014
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sounds like you may have QOS enabled? also did you set channel bandwidth to 20/40?
I know this post is from a long time ago but I recently resolved the problem.

I recently upgraded to Win10 and discovered the setting "Receive Window Autotuning Level" was set to Disabled. I have no idea if this is the same setting in Win8.1(it probably is) but it seems to have been the culprit. I set it back to Normal and now everything works at speed again. I have no idea why it was disabled, or what would have disabled it, or anything else about it, but turning it back on fixed the problem. Not one single tech guy even thought to look at it, because why would it be disabled? Anyway, that fixed it, hope this helps someone having a similar internet slowdown they can't explain.
 

Mr.Spock

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Dec 8, 2019
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So I've got the aforementioned router, and I've seen it get ~200mbps over the wifi on this exact same setup, but after doing a factory reset and installing Merlin onto it, I can't get wifi above 100mbps, like it's limited somehow. Clearing NVRAM manually over telnet hasn't fixed the issue, neither has going back to the original ASUS firmware. I've got no idea what the problem could be and I'd really appreciate some help. Let me know if there's any more information that's needed, I'll happily provide it.

Edit: I should add that when plugging my laptop directly into the cable modem I get full speed of ~200mbps down, but through my router every device, wired and wireless, caps out at 100mbps over 5g/wired and 50mbps over 2.4g.
sounds like you may have QOS enabled? also did you set channel bandwidth to 20/40?
 
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JustSomeNumbers

Honorable
Jan 22, 2014
57
0
10,560
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sounds like you may have QOS enabled? also did you set channel bandwidth to 20/40?
I know this post is from a long time ago but I recently resolved the problem.

I recently upgraded to Win10 and discovered the setting "Receive Window Autotuning Level" was set to Disabled. I have no idea if this is the same setting in Win8.1(it probably is) but it seems to have been the culprit. I set it back to Normal and now everything works at speed again. I have no idea why it was disabled, or what would have disabled it, or anything else about it, but turning it back on fixed the problem. Not one single tech guy even thought to look at it, because why would it be disabled? Anyway, that fixed it, hope this helps someone having a similar internet slowdown they can't explain.
 

Mr.Spock

Prominent
Dec 8, 2019
521
55
590
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that would only fix the Win10 system, but you indicated it happened for all devices connected ?

I know this post is from a long time ago but I recently resolved the problem.

I recently upgraded to Win10 and discovered the setting "Receive Window Autotuning Level" was set to Disabled. I have no idea if this is the same setting in Win8.1(it probably is) but it seems to have been the culprit. I set it back to Normal and now everything works at speed again. I have no idea why it was disabled, or what would have disabled it, or anything else about it, but turning it back on fixed the problem. Not one single tech guy even thought to look at it, because why would it be disabled? Anyway, that fixed it, hope this helps someone having a similar internet slowdown they can't explain.
 

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