ASUS RT-AX58U 5 GHz Packet Loss and TCP Stalls

[underdose]

Hi all. I’m encountering persistent issues with the 5 GHz radio on my ASUS RT-AX58U running Asuswrt-Merlin 388.9_2. It all started somewhere between 388.9 and 388.9_2 but I believe that's just coincidence since nothing has changed regarding wireless drivers.

• 2.4 GHz band is flawless (no packet loss or disconnections).
• 5 GHz band causes random disconnections, high packet loss, and TCP stalls.
• On Google Meet and Slack Huddles I get frequent dropouts.

Some observations:

• Wi-Fi strength is excellent (-33 dBm RSSI, -89 dBm noise).
• iperf3 TCP test (MacBook M1 → router):
  • Consistent throughput dips, multiple full stalls (0.00 Mbps) lasting several seconds.
• iperf3 UDP test at 300 Mbps:
  • 0% packet loss, perfect transfer.
• iperf3 UDP test at 150 Mbps:
  • ~4.7% packet loss (36,901 packets lost out of 776,947).
• mtr also shows high packet loss
• No thermal issues (both bands are 46C)
• Nothing suspicious in the logs

What I've tried so far:

• Fixed 5Ghz channels (36/44)
• Wireless Mode: Auto (was AX only)
• Disabled features (WiFi 6 mode, beamforming, MU-MIMO, Airtime Fairness, QoS)
• Toggling the 5 GHz radio off/on
• Factory reset
• Minimal configuration
• Downgrading to previous Merlin firmware (388.8_4)

which made no difference.

My 5Ghz settings are as below:

I’m wondering if this is a hardware failure (5 GHz radio dying).

Has anyone experienced similar behavior on their AX58U or related models? Any ideas on further tests or hidden settings I might have missed?

 

[Volt]

Regarding UDP, this is not a reliable test per se, packet loss is absolutely normal in this case. I've seen constant UDP packet loss in iperf on fully functional routers. There are many possible causes for this: rate limits, buffer limits, or some form of flood protection. That's why you may be getting zero packet loss on 2.4 and packet loss on 5.

 

[underdose]

Regarding UDP, this is not a reliable test per se, packet loss is absolutely normal in this case. I've seen constant UDP packet loss in iperf on fully functional routers. There are many possible causes for this: rate limits, buffer limits, or some form of flood protection. That's why you may be getting zero packet loss on 2.4 and packet loss on 5.

Thank you for the reply. I’m seeing significant packet loss with both MTR and ping tests, and frequent stutters/rubberbanding during online video and voice apps like Google Meet, Slack Huddles, and Zoom meetings. Could you suggest any additional tests or specific firmware/nvram settings to examine for diagnosing 5GHz issues?

 

[dave14305]

This reminded me of an issue I read about elsewhere affecting Macs. Not sure if it applies here.

Recent Apple updates leading to Wi-Fi issues

Meter is currently tracking an issue that is affecting M1/M2 Macbooks and leading to slow internet connection, drops in Zoom calls, and entirely losing a Wi-Fi connection.

www.meter.com

 

[Volt]

Thank you for the reply. I’m seeing significant packet loss with both MTR and ping tests, and frequent stutters/rubberbanding during online video and voice apps like Google Meet, Slack Huddles, and Zoom meetings. Could you suggest any additional tests or specific firmware/nvram settings to examine for diagnosing 5GHz issues?

I would start troubleshooting by connecting via Ethernet (if possible) with the same client where you experience the issues most frequently. If everything works fine, I would reset the router and try using it for a couple of days with the default WiFi settings.

 

[AlbumMan]

I have an RT-AX3000 (same as your 58U) but now using it as a node when getting an RT-AX86UPro. Here is a screenshot from my 5G Pro settings while back on 388.8_2.
For my neighborhood, I use channel 157. The other setting, OFDMA/802.11ax MU-MIMO, is set to DISABLED. There is also a new ASUS release for this model if you want to try. It primarily fixes some IoT things which is not really your issue. I have a simple network and do not use scripts, etc so not sure if this would something easy to try..