Asus RT-AX88U internet speed slows down after a few days

[scandalous]

I use scMerlin for some specific things, and not very often at that, but yes it works, see below...

"if I understand you correctly, there's no need if I use the scMerlin addon correct? The same settings will be exposed that I need to turn off as highlighted in your first screenshot?"
Yes!, at least it did for me back when I dealt with this early on in the 388.x life cycle. I don't remember if AiProtection had an impact as I never really enabled for any significant length of time.

I have accepted the EULA and Not Withdrawn Consent as I use their DDNS service, for what it's worth.

In in going back an forth between firmwares I did WPS resets which is why it drove me nuts (because I did the nodes as well, and had to rebuild AiMesh every single time). I did remember messing with those paramters at some point before I started having problemd, but I did have QoS disabled, so I thought no harm no foul when I stumbled upon it I unchecked everything as shown and set all the other parameters to 100%. But I do remeber quite vividly the moment I unchecked ACK, SYN and FIN and hit apply and saw my bandwidth (as measured via SpeedTest on the router) return to my normal and stay there.

As for it running on an AX88u on 388.9, here you go, and see my signature...
View attachment 65317

So I'm back to report that unfortunately your recommendations did not work. The speed halved a couple hours later. I looked through the logs as well, but I don't see anything out of the ordinary. Just some handshakes etc.

Standard reminder. If you are having speed issues. If you have enabled any of the AiProtection, TrendMicro features or any feature that utilizes either, you should disable those features (all of them) then withdraw from them on the Administration > Privacy (or Policy) page. Just disabling them isn't enough, you have to also withdraw permission for them on the Privacy/Policy page as well. Otherwise they may still run in the background. Then test to see if the issue continues.

When all else fails, perform a hard factory reset then a basic manual configuration (do not import a saved router.cfg file or attach a USB hard drive to the router). Don't enable extra features beyond the basics to get the router up and running. Don't add any addon scripts. Test the router as bear as possible after a reset to troubleshoot.

This also made no difference, the issue still occurs.

Just for giggles, if you have a CAT 6 cable handy, try that between the ONT and the Asus router. CAT7 is more sensitive to imperfections in the termination and receptacle.

If you want to run speed tests, they should be run from lan client device and not the router. Generally, not reasonably accurate when run on the router due to the CPU load.

I tried the cat6 cable and that made no difference either.

Well, you certainly getting a lot of advice... some sound and some just noise. In reality, your router should be able to run at the default settings just fine. Even with the Trend Micro features enabled! Messing with the WIFI settings can cause more issues.
As for the PPPoE MTU I mentioned before, the setting is generally recommended to be 1492 bytes. Some feel that this will slow the bandwidth when in fact it can improve it as fragmentation will be reduced. It may be worth your while to try it.
Yes, there can be other factors. Custom firmware included (I do not want to knock the Merlin effort and I have run his firmware off and on for years with good results). Going back to the factory firmware and running simple configuration should be a first start.

I appreciate all advice coming my way. I'll be trying the MTU set to 1492 next. If that doesn't work, I'll go back to the stock firmware and report back as soon as I can.

 

[scandalous]

Well, you certainly getting a lot of advice... some sound and some just noise. In reality, your router should be able to run at the default settings just fine. Even with the Trend Micro features enabled! Messing with the WIFI settings can cause more issues.
As for the PPPoE MTU I mentioned before, the setting is generally recommended to be 1492 bytes. Some feel that this will slow the bandwidth when in fact it can improve it as fragmentation will be reduced. It may be worth your while to try it.
Yes, there can be other factors. Custom firmware included (I do not want to knock the Merlin effort and I have run his firmware off and on for years with good results). Going back to the factory firmware and running simple configuration should be a first start.

Just wanted to confirm that the MTU default setting did not solve the problem. The issue is here again after I changed the setting and rebooted.

 

[degrub]

Does that router have an alternate LAN port that can be used for WAN ?

 

[scandalous]

Does that router have an alternate LAN port that can be used for WAN ?

Unfortunately it does not. I've consider a broken WAN port, but would find it really weird that it could work for up to 48 hours sometimes and then totally drop. If the issue persists on the stock Asus firmware, I'll consider it a hardware defect and get a new device.

 

[FernandoF]

@scandalous, if you want to try an alternate LAN port that can be used for WAN, there's a trick you can take advantage of:

1. Go to WAN > Dual WAN
2. Set "Enable Dual WAN" to ON
3. Choose a "Primary WAN" port that's different than the regular WAN port. The recommendation is to use LAN 1-4, as LAN 5-8 seem to be problematic with the RT-AX88U
4. You can probably set the "Secondary WAN" with the regular WAN port - it won't be used anyway
5. Leave the other fields untouched and Apply - the router will reboot
6. During the reboot, switch your WAN ethernet cable from the regular WAN port to the LAN port you selected in #3
7. After the reboot, go to WAN > Internet Connection, select the "WAN Type" to match the same LAN port from #3 and #6, adjust the other WAN fields properly (as little as possible), and Apply
8. Reboot

In case you do have a broken WAN port, the above may help. Good luck!

 

[scandalous]

@scandalous, if you want to try an alternate LAN port that can be used for WAN, there's a trick you can take advantage of:

1. Go to WAN > Dual WAN
2. Set "Enable Dual WAN" to ON
3. Choose a "Primary WAN" port that's different than the regular WAN port. The recommendation is to use LAN 1-4, as LAN 5-8 seem to be problematic with the RT-AX88U
4. You can probably set the "Secondary WAN" with the regular WAN port - it won't be used anyway
5. Leave the other fields untouched and Apply - the router will reboot
6. During the reboot, switch your WAN ethernet cable from the regular WAN port to the LAN port you selected in #3
7. After the reboot, go to WAN > Internet Connection, select the "WAN Type" to match the same LAN port from #3 and #6, adjust the other WAN fields properly (as little as possible), and Apply
8. Reboot

In case you do have a broken WAN port, the above may help. Good luck!

Thank you for your tip! I haven't been able to read the replies in a few days. I'll try this now! I've been running the ISP modem for a while and that has worked just fine in terms of speed.

I've also tried the stock firmware and the new merlin firmware that came out a few days ago to no avail. I'll report back after I've tried the WAN configuration.

 

[scandalous]

@scandalous, if you want to try an alternate LAN port that can be used for WAN, there's a trick you can take advantage of:

1. Go to WAN > Dual WAN
2. Set "Enable Dual WAN" to ON
3. Choose a "Primary WAN" port that's different than the regular WAN port. The recommendation is to use LAN 1-4, as LAN 5-8 seem to be problematic with the RT-AX88U
4. You can probably set the "Secondary WAN" with the regular WAN port - it won't be used anyway
5. Leave the other fields untouched and Apply - the router will reboot
6. During the reboot, switch your WAN ethernet cable from the regular WAN port to the LAN port you selected in #3
7. After the reboot, go to WAN > Internet Connection, select the "WAN Type" to match the same LAN port from #3 and #6, adjust the other WAN fields properly (as little as possible), and Apply
8. Reboot

In case you do have a broken WAN port, the above may help. Good luck!

Could you walk me through a little better?

I've configured this as you instructed, the part I get stuck on is the IPTV section. Normally after configuring the WAN/PPPoE, I then go LAN > IPTV and enter 6 in the internet section there to get my internet up and running.
After following your instructions I have no internet. I cannot enter anything in the port 3 section under the IPTV tab as it gives me an error "WAN and IPTV cannot be on the same port". So I'm a little confused as to how I'm supposed to get this to work.
I'm probably being stupid and missing something simple. Any insight?

 

[Elmer]

Hi,

For the last few weeks I've been having an issue with my AX88U where me internet connection slows down considerably. My gigabit speeds go down about half (or lower) and only a reboot fixes the issue. I check this via internal speedtest tool but also directly via the speedtest.net website.
The problem presents itself via Wi-Fi and my wired devices (exact same speed, regardless of device). I've currently set up a reboot scheduler in the night to negate the issue, but I don't think this is a permanent solution and would like to know where the issue stems from.
The speed itself is a bit inconsistent, where it can be a little higher or lower but never reaches the full gigabit speeds until a reboot.

Some setup information and history.

- I have a gigabit connection that I've had for 2 years from the same provider. My WAN IP has not changed in all that time.
- My AX88U is connected to an ONT via a cat7 (all my cables are cat7 for future upgrades) and acts as my modem/router. It's been running Merlin since I bought it and is currently on "RT-AX88U_3004_388.9_0". I've dirty upgraded ever since I got the router a couple of years ago, without issues.
- I have the following devices connected via cable to the router:
1. Synology NAS
2. ASUS ZenWIFI XD6, which is setup as a NODE elsewhere in my home. Connected to this node are a desktop PC and a PS5 via cable as well. The XD6 runs the latest firmware.

I haven't done anything that interesting in terms of configuration. Up until a month ago this was my setup:
- For the WAN I configured the PPPoE for the internet connection. DNS is currently set to Cloudfare with Google as a secondary.
- Regular (separated) Wi-Fi setup for 5Ghz and 2.4GHz bands.
- For the LAN I've set up MAC reservations for every device in my home and limited the IP pool to what I currently need.
- Have a Wireguard VPN server running for when I'm abroad so I can connect to home.

A month ago I made the following small changes:
- I enabled guest-Wi-Fi #3 for the 2.4ghz band (#1 acted weird for some reason) to disallow access to intranet.
- I configured a Wireguard VPN client with a Proton VPN config. I have two devices in the network that go out this way.

What I've tried and checked:
- Note; every change I made was followed by a reboot because no config change actually (not even temporarily) solved the problem. I waited to make sure the issue presented itself again and then tried something else.
I don't have an exact timeline on how long it takes before the issue presents itself. But it's somewhere in the span of 24-48 hours.

1. I assumed the issue might lie with my configuration changes. So I reverted everything as it had been running for the last 2 years, prior to my changes. Meaning disabling the guest network and disabling the VPN client. No luck, the issue still persisted.
2. I rolled back to the previous firmware ( "RT-AX88U_3004_388.8_4"), first with the changes enabled and then without.
3. I did a full factory reset for both the router and the node, configured everything manually, without the VPN client and guest Wi-Fi, but no luck still. I tried this on both the previous and latest firmware.
4. I re-did step 3, but now with all my devices disconnected and only my desktop connected via cable. I also repeated this step but only with my laptop connected via cable and then again with my phone via Wi-Fi. I wanted to ensure that it wasn't some device or negotiation issue. Everything also presented as 1gbit if connected via cable.
5. I re-did step 3 and now with no configuration changes except for the PPPoE setup and still have the same issue.
6. I tried a different ONT with no luck.
7. I googled around to see if I could find people with the same issues. While they weren't exactly the same, I tried changing some of the things suggested like different DNS, making sure QOS was disabled, DDNS was off, AI protection was off, hw-acceleration was enabled. But most of these things are set like that by default. I also left the router off for a couple of hours.
8. The temp of the router is aprox. 60 degrees Celsius. The RAM also doesn't fill up and is below 50% usage, even when the issue occurs. There's no traffic (very low KB/s) to be seen unless I'm doing something, so nothing is clogging up my connection. CPU usage is near near 0% if I'm not doing anything. During a speedtest, core 1 shoots up to 100%. The rest doesn't do anything.
9. EDIT: I forgot to add that I also tried different LAN ports on the router just in case. Didn't make a difference and it seemed unlikely to be the issue since the problem also presents itself on Wi-Fi. I also swapped out the cable between the router and ONT.

I considered it to be a throttling issue, but my provider has confirmed that not to be the case. Like I mentioned before, a reboot solves it and it works for a day or maybe 2, which makes me wonder if it's an actual configuration issue. I also don't see anyone posting about it on the forum, which makes it unlikely to be a bug in the firmware.

I hope someone could help me further into solving this as I'm not quite sure on what to do next.

Same problem. I just did the auto-reboot once every three days in the middle of the night. With mine, I noticed that the memory would slowly edge up to the 1G ram and that's when things slowed down. The reboot dropped it down to a 925 and the then the process would begin again. I notice you said that ram was not the problem, but perhaps it is dhcp reservations not dropping? Might want to try the AMTM dhcp app. I went to a 2G router model and am having smooth sailing, but a two or three day auto-reboot worked fine till I switched.

 

[scandalous]

Same problem. I just did the auto-reboot once every three days in the middle of the night. With mine, I noticed that the memory would slowly edge up to the 1G ram and that's when things slowed down. The reboot dropped it down to a 925 and the then the process would begin again. I notice you said that ram was not the problem, but perhaps it is dhcp reservations not dropping? Might want to try the AMTM dhcp app. I went to a 2G router model and am having smooth sailing, but a two or three day auto-reboot worked fine till I switched.

It's definitely not the ram for me. I checked the CPU and RAM on multiple occasions. The ram never exceeds even 50% of the total capacity. I don't think it has anything to do with the reservations. I ran the router fully stock (besides the PPPoE config for internet) and the problem still persisted. I'm just beginning to think it's a hardware issue. The problem presents itself on both Merlin and stock firmware, with no config changes. The ISP router works fine, meaning the problem is not outside of my home, the cabling or ONT; basically everything before the router.

I've ordered a RT-BE88U and will run that for a week to see how that goes.

 

[ApexRon]

I read through all the posts but I need to recap where I believe you’re currently at. With the physical setup of ONT <—-> ASUS the internet speed appears to half after a period of time with an ASUS reboot resolving at least until the same period of time passes. With a physical setup of ONT <—-> ISP device <—-> ASUS there is no issue. Am I correct?

If use of the ISP device resolves the issue, what function does the ISP device provide? Modem/router?

More than a decade ago I had similar symptoms but it turned out it wasn’t the network speed that was halved. It was the fact that that my ISP didn’t like the MAC address of my router and periodically the ISP’s security monitoring would kick in release the my router’s MAC address was not known resulting in the ISP flooding my router with some sort of low layer protocol effectively halving my data speed. And rebooting my router at the time would temporarily resolve. For me the solution was to leave the ISP’s modem/router in place (I was able to disable its WiFi) and cascade my router off of it. Eventually I moved to a different ISP and no more issues.