RT-AX86U Pro firmware upgrade failed

[liug]

I have RT-AX86U Pro currently running RT-AX86U_PRO_3006_102.4_beta2.

A few days ago I saw beta3 out. I downloaded it but failed to upgrade my router. Today I saw 3006_102.4 is released. I downloaded but upgrade also failed. I tried Firefox, Chrome and Safari from my Mac, and all gave:

First: Please wait , applying settings
Later: Firmware upgrade unsuccessful. This may result from incorrect image or error transmission. Please check the version of firmware and try again.

I verified the unzipped file RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb matching sha256sum 7ac1326e76ec8654eb4e08e93815179f88cf72c29433717f2a8cc3eae609499d

 

[ExtremeFiretop]

This may sound obvious, but you didn't mention it anywhere in your thread.
Have you tried unplugging any USB devices from the router and rebooting it before doing the firmware upgrade?

You can also try to use the MerlinAU addon from amtm to trigger the upgrade since it's automated from the router, and pumps out logs with important details if it fails.

 

[liug]

There is no USB devices attached to the router.

When the first upgrade failed, the router self rebooted, before I can use the different browsers to try again. This means at least the second or third browser upgrade attempts were after the router reboot.

Some additional information: This RT-AX86U Pro runs as AiMesh router and I also have two RT-AC68U running as AiMesh Node. Both RT-AC68U have latest stock Asus firmware 3.0.0.4.386_51733-g8eebcd2. I am not sure if that matters.

 

[ExtremeFiretop]

I am not sure if that matters.

No.

Without any logs, from your syslogs or from MerlinAU; it would be hard for us to guess. The 2 guesses I already made were shots in the dark based on the fact that they were missing steps.
Connect via SSH; type "amtm" and select option 8 for MerlinAU; no USB is required: https://www.snbforums.com/threads/m...to-updater-webui-gnuton-support.91326/page-15

Configure the add-on with your router credentials and trigger the update; if it fails; provide screenshots or logs from your system logs or from MerlinAU.
Finally; if it's still failing after providing logs, you can always try the ASUS rescue tool:

[Wireless Router] How to use Rescue Mode (Firmware Restoration)? | Official Support | ASUS Canada

 

[bbunge]

Your best bet is to do a factory reset, power cycle and a minimum configure. Maybe a hard factory reset. Then do the upgrade. Adding more stuff as recommended could get you in trouble. You may have to go back to Asus firmware then upgrade to Merlin.

Use the Asus recovery tool as a last resort!

 

[ExtremeFiretop]

Adding more stuff as recommended could get you in trouble.

If "Getting in trouble" means screenshots and logs of the flash process... I totally agree! Otherwise nah.

Steps recommended would calmly fail and provide the step or reason in human language for the user. If the flash itself is failing due to a hardware issue we could even narrow that down further.

Also, If it's user error a scripted solution will handle it.

Use the Asus recovery tool as a last resort!

This agreed. Make sure to use the linked steps i provided and report back.

 

[liug]

@ExtremeFiretop I tried your MerlineAU and here is the output:

...​

Resolving cfhcable.dl.sourceforge.net... 146.71.73.5
Connecting to cfhcable.dl.sourceforge.net|146.71.73.5|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 64668708 (62M) [application/octet-stream]
Saving to: '/home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip'

linAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmwar 32%[===================================> /home/root/MerlinAU 100%[===================>] 61.67M 182KB/s in 5m 8s

2025-05-11 10:40:57 (205 KB/s) - '/home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip' saved [64668708/64668708]

Required RAM: 94729 KB - RAM Free: 478016 KB - RAM Available: 544001 KB
-----------------------------------------------------------
Archive: /home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip
Length Date Time Name
--------- ---------- ----- ----
68465104 05-10-2025 12:47 RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb
9622 05-10-2025 11:50 README-merlin.txt
11489 05-10-2025 12:47 Changelog-3006.txt
112 05-10-2025 12:47 sha256sum.sha256
-------- -------
68486327 4 files
-----------------------------------------------------------
Archive: /home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip
inflating: RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb
inflating: Changelog-3006.txt
inflating: sha256sum.sha256
-----------------------------------------------------------
Required RAM: 94729 KB - RAM Free: 473556 KB - RAM Available: 541942 KB
No high-risk phrases found in the changelog file.
Required RAM: 94729 KB - RAM Free: 473260 KB - RAM Available: 541830 KB
No ROG build found. Skipping.
SHA256 signature check for firmware image file passed successfully.
Required RAM: 94729 KB - RAM Free: 473452 KB - RAM Available: 541757 KB
Router Web URL is: https://RT-AX86U_Pro-C8F0.lan:8443
**IMPORTANT**:
The firmware flash is about to start.
Press <Enter> to stop now, or type Y to continue.
Once started, the flashing process CANNOT be interrupted.
Continue? [yY|nN]? y
OK

Restarting web server... Please wait.
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 220 0 84 100 136 3087 4998 --:--:-- --:--:-- --:--:-- 8461
Cron jobs from 3rd-party add-ons were not found.

Flashing RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb...
Please wait for reboot in about 4 minutes or less.

Can't get any disk's information.
Connection to 172.20.20.1 closed by remote host.
Connection to 172.20.20.1 closed.

After router boots, it still shows old beta2.

 

[ExtremeFiretop]

@ExtremeFiretop I tried your MerlineAU and here is the output:

...​

Resolving cfhcable.dl.sourceforge.net... 146.71.73.5
Connecting to cfhcable.dl.sourceforge.net|146.71.73.5|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 64668708 (62M) [application/octet-stream]
Saving to: '/home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip'

linAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmwar 32%[===================================> /home/root/MerlinAU 100%[===================>] 61.67M 182KB/s in 5m 8s

2025-05-11 10:40:57 (205 KB/s) - '/home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip' saved [64668708/64668708]

Required RAM: 94729 KB - RAM Free: 478016 KB - RAM Available: 544001 KB
-----------------------------------------------------------
Archive: /home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip
Length Date Time Name
--------- ---------- ----- ----
68465104 05-10-2025 12:47 RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb
9622 05-10-2025 11:50 README-merlin.txt
11489 05-10-2025 12:47 Changelog-3006.txt
112 05-10-2025 12:47 sha256sum.sha256
-------- -------
68486327 4 files
-----------------------------------------------------------
Archive: /home/root/MerlinAU.d/RT-AX86U_PRO_firmware/RT-AX86U_PRO_firmware.zip
inflating: RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb
inflating: Changelog-3006.txt
inflating: sha256sum.sha256
-----------------------------------------------------------
Required RAM: 94729 KB - RAM Free: 473556 KB - RAM Available: 541942 KB
No high-risk phrases found in the changelog file.
Required RAM: 94729 KB - RAM Free: 473260 KB - RAM Available: 541830 KB
No ROG build found. Skipping.
SHA256 signature check for firmware image file passed successfully.
Required RAM: 94729 KB - RAM Free: 473452 KB - RAM Available: 541757 KB
Router Web URL is: https://RT-AX86U_Pro-C8F0.lan:8443
**IMPORTANT**:
The firmware flash is about to start.
Press <Enter> to stop now, or type Y to continue.
Once started, the flashing process CANNOT be interrupted.
Continue? [yY|nN]? y
OK

Restarting web server... Please wait.
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 220 0 84 100 136 3087 4998 --:--:-- --:--:-- --:--:-- 8461
Cron jobs from 3rd-party add-ons were not found.

Flashing RT-AX86U_PRO_3006_102.4_0_nand_squashfs.pkgtb...
Please wait for reboot in about 4 minutes or less.

Can't get any disk's information.
Connection to 172.20.20.1 closed by remote host.
Connection to 172.20.20.1 closed.

After router boots, it still shows old beta2.

But what does the system logs show? I don't need the MerlinAU logs anymore as it's clear that it didn't stumble anywhere while preparing for the flash.

This means we can rule out a lot of things such as memory issues, SHA issues, other add-ons or scripts, and really any user error.

Can you provide the syslog matching that same time frame as well?

As we suggested you can try the rescue tool. But please if you can send the systemlogs before you do. It would be extremely valuable for educational purposes.

Feel free to DM it if you rather.

 

[liug]

Sent you the DM. Thanks!

 

[bennor]

Some additional information: This RT-AX86U Pro runs as AiMesh router and I also have two RT-AC68U running as AiMesh Node.

A suggestion if you haven't tried already. Disconnect, turn/power them physically off if needed, all devices (wired and wireless including AiMesh nodes) from the RT-AX86U Pro other than a single wired computer. Reboot the router, then try to update it's firmware. Another thing to check, disable any browser extensions/add-ons. Also temporarily disable any security/antivirus software running on the computer as a troubleshooting step.

 

[liug]

Just to close the loop here. @ExtremeFiretop helped me over DM and the issue turned out to be the bad blocks on the NAND chip caused the overall usable size can't fit the new firmware. This is similar to this other thread: Unable to flash firmware due to bad blocks

While checking if warranty is still valid, I am flashing back the
latest stock asus firmware 3.0.0.6.102_34349 downloaded from
https://www.asus.com/us/networking-...86u-pro/helpdesk_bios?model2Name=RT-AX86U-Pro This firmware is small enough and didn't complain during upgrade.