AC86U 5Ghz internet speed much slower out of nowhere

[brainosas]

Hello guys,

I have AC-RT86U unit running on Merlin firmware 386.10 apha 1 firmware. Just two weeks ago all was good - 5 Ghz speed recently plummeted to 640 Mbit (tested with Iphone 12 Pro Max and I have 1 Gb download/upload plan). This was the best ever result. Then, suddenly I'm only getting third of that speed, sometimes - half the speed on same phone. Same on any other devices - various Iphones, MacBooks - on 5 Ghz network speed rarely exceeds 300 Mbit (was around 700 Mbit on MacBook). I did not change anything in my network configuration recently and so this change in performance is very unexcpected. If I test internet speed via Speedtest on my PC via wired connection, it still shows usual results: 920 Mbit for download and 840 for upload. I also tested link speed via Iphone Wi-FiSweetSpots app, which also shows great speed - around 700 Mbit, but when it comes to wireless internet speed, it's gone. Previously, if I would get around 540 Mbit speed on my Iphone during evenings, when neighbours are back at home, I would treat this as a bad result. Now, it usually does not exceed 130 - 240 Mbit - and that is next to router, few meters away. My router still sits in the same place - on the fridge where it always was. All wireless speed tests I perform few meters away from it, no whatsoever obstructions in a way.
I then started fiddling with various wifi settings on the router, installed 386.11 firmware, same results even after factory reset. I have to say I do not use any special feature on the router - no any usb connected, no entware, scripts, no QoS, VPN, nothing at all. Just bacic functions and port forwarding for RealVNC to work.

I will attach few screenshots with the settings, maybe you will be able to provide insights what might have gone wrong with my setup. I fell of the bike last Sunday, now as I hardly can walk, I have time for this issue

 

[brainosas]

OMG. Completely forgot - I've bought same used RT-AC86U router (found it cheap), thinking maybe it will help - absolutely same results.

 

[Jaime Alvarez]

OMG. Completely forgot - I've bought same used RT-AC86U router (found it cheap), thinking maybe it will help - absolutely same results.

Have you checked if your fixed channel got some new interference? Fire up the site survey and see. If channel 36 is too crowded it would be a likely cause.

 

[brainosas]

Have you checked if your fixed channel got some new interference? Fire up the site survey and see. If channel 36 is too crowded it would be a likely cause.

Partially it could have been the reason - there are seven other networks on channel 36, I have changed to 56 and now there is only one another network but it did not help (much). Speed is still under 300 Mbit which I have never observed even during peak loads that typically happen during evenings. Thank you for the tip though.

 

[Jaime Alvarez]

I just noticed (probably unrelated to your speed issue) that you have port forwarding for VNC. If i am understanding correctly, this is a security risk, I'd recommend setting an OpenVPN server in your router and connect through VNC using the local intranet.

 

[Sonyrolfy]

I did noticed this too on Iphones, Mac's. I cant place the slowdown other then IOS updates or some script on the router causing the slowdown. I didnt test disabling scripts or forget network settings on phone. But i did read someting about IOS updates and slow wifi..

 

[Turgut Kalfaoglu]

I did noticed this too on Iphones, Mac's. I cant place the slowdown other then IOS updates or some script on the router causing the slowdown. I didnt test disabling scripts or forget network settings on phone. But i did read someting about IOS updates and slow wifi..

they probably want you to upgrade your phone

 

[brainosas]

It now does not matter which device I'm using to meter speed - speed has dropped twice on all wireless devices.

 

[heysoundude]

You're probably not going to like reading this, but -
It's often helpful after upgrading to do a hard reset.
Further, the hardware itself is getting older, and it may be showing you that it may need to be replaced and retired soon.

Before you do a full nuke of the router and start from scratch, have you tried power cycling it and the modem?
Also - try Enabling the 802.11ac beamforming option...don't forget to hit apply

 

[brainosas]

You're probably not going to like reading this, but -
It's often helpful after upgrading to do a hard reset.
Further, the hardware itself is getting older, and it may be showing you that it may need to be replaced and retired soon.

Before you do a full nuke of the router and start from scratch, have you tried power cycling it and the modem?
Also - try Enabling the 802.11ac beamforming option...don't forget to hit apply

I did hard reset already ten times probably. Tried beamforming as well. And, please pay attention, I do have another exactly same router which gives me exactly same results. And first of all, I did not alter any settings for quite a long time, much longer before I started noticing the drop out in speed. And I didn't tell my setup - it is a fiber optics cable incoming to my apartment, then it is a converter and from converter the signal goes to router.

 

[heysoundude]

OK - that's really great. I wish I had fibre to my home.
Take a breath and contain your frustration...we'll get to the bottom of the issue together.
My initial suspicion is that you may have overlooked (or can't remember changing a setting, or are unaware of) something in the config that has changed, and must be changed back to the way it was.
Eventhough you may not have altered the settings, firmware upgrades can do that for you, like it or not. Resetting ensures you're at factory default so that you can better tune your machine to optimal.
what we need to focus on is what is different between now and then...and it's probably something that often gets overlooked or taken for granted.

How does your ISP suggest you config your machine to use their network? have they enabled ipv6, and should you do the same?

 

[brainosas]

OK - that's really great. I wish I had fibre to my home.
Take a breath and contain your frustration...we'll get to the bottom of the issue together.
My initial suspicion is that you may have overlooked (or can't remember changing a setting, or are unaware of) something in the config that has changed, and must be changed back to the way it was.
Eventhough you may not have altered the settings, firmware upgrades can do that for you, like it or not. Resetting ensures you're at factory default so that you can better tune your machine to optimal.
what we need to focus on is what is different between now and then...and it's probably something that often gets overlooked or taken for granted.

How does your ISP suggest you config your machine to use their network? have they enabled ipv6, and should you do the same?

No ipv6 here, I just enable Automatic IP and that's it. No passwords, nothing. This part always works well. I also tried, after resetting router, adjust settings very minimally - basically wifi only (SSID name plus password, plus channel). This does not solve the problem.

 

[degrub]

anyone done a wireless survey ? maybe you have a neighbor with a new ASUS router blasting you out ?
Also, there have been repeated issues with TVs or other IOTs causing severe degradation in wireless bandwidth by swamping the channel with packets. Sony was a recent example discussed in the forums here.

 

[brainosas]

anyone done a wireless survey ? maybe you have a neighbor with a new ASUS router blasting you out ?
Also, there have been repeated issues with TVs or other IOTs causing severe degradation in wireless bandwidth by swamping the channel with packets. Sony was a recent example discussed in the forums here.

I've done wireless survey, changed channel, did not help, sadly. There are no other Asus routers from what I see and signals are quite weak.

 

[Jaime Alvarez]

This guide by @L&LD might be helpful. If nothing works then I'd go for the nuclear reset that is linked at the bottom...

Troubleshooting 101 Asus/RMerlin Routers 2020

Top 10 Simple Asus/RMerlin firmware powered Router Troubleshooting steps to try first: NOTE: Although this is for Asus/RMerlin-firmware powered routers, the steps below may be relevant to all routers, to get to a quick fix for common symptoms. Check that the router’s System Time is accurate on...

www.snbforums.com

 

[iJorgen]

Any difference if Enabling this?

What's your Noise-levels?! (shown under System Log->Wireless Log)

 

[brainosas]

Any difference if Enabling this?
View attachment 50765

What's your Noise-levels?! (shown under System Log->Wireless Log)
View attachment 50766

Enabling MIMO does not have any visi ke effect. Here’s screenshot of noise levels :

 

[drinkingbird]

I've done wireless survey, changed channel, did not help, sadly. There are no other Asus routers from what I see and signals are quite weak.

Have you ensured that universal beamforming is disabled?

It is also possible that whatever IOS update happened, your apple devices are now flooding out a lot more MDNS or something. It seems to have happened around the same time as IOS update so that's something to focus on. If you temporarily change your SSID and just connect one device like a laptop, do things improve?

 

[brainosas]

Ok, I've asked my ISP to send their specialist. He will also bring another AC router to check the results. This will happen on Friday, I will post an update here afterwards.

 

[drinkingbird]

Ok, I've asked my ISP to send their specialist. He will also bring another AC router to check the results. This will happen on Friday, I will post an update here afterwards.

If wired speeds are good, it's not an ISP issue. Did you try the two things I suggested?