Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage

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Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage

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Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-17 03:52:04 - last edited 2023-03-01 18:14:28
Model: Archer AX21  
Hardware Version: V1
Firmware Version: 1.3.6 Build 20221125 rel.68607(5553)

As the title reads, my Archer AX21 hardware revision v1.26 (The Web UI says v1.20 but the bottom sticker on the router says v1.26 so I am putting v1.26 as it seems both revisions may use the same firmware which is why it is reporting v1.20 and not v1.26) in Access Point Mode will effectively die after an indeterminate amount of time (13 hours to 20 minutes) even with nothing going on.


What I mean by that is, the devices will get disconnected from the WiFi network and the web ui will not be able to be accessed until a restart is performed, I am able to monitor this by pinging the device and for my logging, it is pinged every 15 seconds and that is how I got the figures of 13 hours to ~20 minutes, it is important to note, the 20 minutes of runtime was after the previous 13 hour deadlock, it was in that state (deadlock) for 16 hours before being rebooted, firmware updated and then going down after 20 minutes of uptime, It is likely not my Router (running OPNsense) or Switch (running OpenWrt) as if that were the case, my ethernet devices would cease getting internet or have issues but it is only the Archer AX21 and furthermore, my switch is an Archer C7 v4 AC1750 and it works perfectly fine even now as both a Switch and an AP (when the issues arised, the WiFi was either not on, on the AX21 or the WiFi was disabled on my Archer C7 v4 so the Archer C7 should not be affecting anything).

 

Here is the ping history for the AX21 after having a few days of not being used:
Configuration: Router powered on and connected to internet via the WAN port (no 5G or 2.4G network enabled and no ethernet/switch devices connected, so it should be doing nothing):
654275febe6f4c93abf7e7a2a137e146

 

Here is the ping history for the AX21 after being rebooted after 16 hours of being in the deadlocked state (as I am calling it) and getting a reflash of the firmware from TP-Link's website:
Configuration: Same as previous but the firmware was reflashed:
e8656850e1e34ddcb1dc43f84396d0c1

 

I am assuming it could be thermal related (and that in the deadlocked state, it may still be trying to do work but stuck (needs to be true for my thermal theory to be correct)) although unfortunately, it appears that the Web UI of the AX21 does not report CPU temperatures and even if it did, it seems that TP-Link does some annoying obfuscation/encryption so it is not easy to directly get the values from an http request so it can be easily monitored/logged. (My mistake for going for a device that does not seem to have good custom firmware support which makes it 100x harder to debug)

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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-20 12:18:49 - last edited 2023-03-01 18:14:28

Hello @JordanPlayz158 

 

If I understand your description correctly, is the network layout as below?

 

Router (running OPNsense, wifi is disabled) --- Switch (Archer C7 v4, running OpenWrt, wifi is disabled) --- AX21 (AP mode)

 

How did you configure the AX21 as an Access Point? Case 1 or Case 2 as per this guide?

 

Is it possible to connect the AX21 to the main router directly bypassing the Switch? Will it behave the same?

 

What are the IP addresses of these three devices, the Router, Switch, and AX21? Are the Switch and AX21 both using static IP addresses? If not, please try to assign static IP addresses for both of them and ensure they are in the same IP subnet of the main router, then monitor the connectivity again.

Nice to Meet You in Our TP-Link Community. Check Out the Latest Posts: Connect TP-Link Archer BE550 to Germany's DS-Lite (Dual Stack Lite) Internet via WAN Archer GE550 - BE9300 Tri-Band Wi-Fi 7 Gaming Router EasyMesh Is Available When Wi-Fi Routers Work in AP Mode as A Controller. Archer AX90 New Firmware Added Support for EasyMesh and Ethernet Backhaul If you found a post or response helpful, please click Helpful (arrow pointing upward icon). If you are the author of a topic, remember to mark a helpful reply as the "Recommended Solution" (star icon) so that others can benefit from it.
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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-20 17:13:51

  @Kevin_Z 

 

"If I understand your description correctly, is the network layout as below?

 

Router (running OPNsense, wifi is disabled) --- Switch (Archer C7 v4, running OpenWrt, wifi is disabled) --- AX21 (AP mode)"

Yes, that is correct (that would be the condition it will be working in once/if I can get it reliable)

 

 

"How did you configure the AX21 as an Access Point? Case 1 or Case 2 as per this guide?"

I configured the AX21 as an Access Point via Case 1, switching the operation mode

 

 

"Is it possible to connect the AX21 to the main router directly bypassing the Switch? Will it behave the same?"

I will attempt that.

 

 

"What are the IP addresses of these three devices, the Router, Switch, and AX21? Are the Switch and AX21 both using static IP addresses? If not, please try to assign static IP addresses for both of them and ensure they are in the same IP subnet of the main router, then monitor the connectivity again."

The router is using 192.168.1.1, the Switch is using 192.168.1.2 and the AX21 is using 192.168.1.3, all static ips (and are out of the range of the DHCP pool, the pool starts at 192.168.1.100 to 192.168.1.200)

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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-21 18:45:32 - last edited 2023-02-23 15:36:53

I don't want to Jynx it but it has been 24 hours (probably won't feel safe until 48 hours) and no crash. If it is indeed fixed (and I hope it is), do you know any reason why connecting it through the Switch would cause a crash but connecting it directly to the router would not? I ruled the switch out as a possibility as every other device connected to it works perfectly fine but perhaps there might be something wrong with the switch or the firmware on the AX21?

 

Edit: it has now been 48 hours and it has not crashed (a good sign), I have now enabled WiFi 2.4G + WiFi 5G (it was only routing packets for the 48 hours so adding more load as I plan to use it in this scenerio and it is no doubt more intensive than routing packets)

Edit 2: it has been ~72 hours (24 hours after WiFi 2.4G and 5G activated) and still stable, I think it is fixed but that is still baffling to why that change would change anything?

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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-24 09:19:51

@JordanPlayz158 

 

I'm happy to hear that the network is working properly bypassing the switch.

 

I cannot explain why this helps, I assume that there might be some special settings on the switch that cause issue with the AX21. But I cannot say that for sure since we didn't troubleshoot or analyze the settings on it.

Nice to Meet You in Our TP-Link Community. Check Out the Latest Posts: Connect TP-Link Archer BE550 to Germany's DS-Lite (Dual Stack Lite) Internet via WAN Archer GE550 - BE9300 Tri-Band Wi-Fi 7 Gaming Router EasyMesh Is Available When Wi-Fi Routers Work in AP Mode as A Controller. Archer AX90 New Firmware Added Support for EasyMesh and Ethernet Backhaul If you found a post or response helpful, please click Helpful (arrow pointing upward icon). If you are the author of a topic, remember to mark a helpful reply as the "Recommended Solution" (star icon) so that others can benefit from it.
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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-02-28 20:55:49 - last edited 2023-02-28 21:52:50

  @Kevin_Z This may be unrelated but sad to say, after 8 days of uptime, it crashed, although rebooting the AP every 8 days I guess is acceptable (if it is consistent) but definitely not desirable.

 

Edit: it is not consistent, after rebooting after the crash after 8 days, it took 1 hour to crash again, this time interestingly it might've noticed it was in a failed state as it rebooted entirely on its own but after this automated reboot, the AP only survived for a staggering minute so it is not viable even after bypassing the switch.

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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-03-31 04:39:33

  @Kevin_Z I have now removed the Switch and the pfSense router from my setup and have the router running in the normal operating mode (router mode, not ap mode) but there still seems to be an issue, it locks up. Unfortunately even with UART connected to the router, there is no error, no stacktrace in the output and after reviewing the firmware from the website for my router with `binwalk`, I see that there is no valid password set for any of them and for those without a password `guest` the shell is not valid, so I have no way of getting a shell inside the device to get more information and possible confirmation for my theories, one of which is a thermal theory, it overheats but it doesn't make sense that the device wouldn't just restart or shut down linux properly. Here is the log from UART of the startup to the crash and the subsequent restart (in case the device can detect a failed state from last boot but that doesn't appear to be the case)

 

htt ps://pastebin. com/N7yHugaB (I needed to split up the link as it is impractical to paste it all in (I did try but "illegal links filter") and links filter)

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Re:Archer AX21 v1.26 - Router (AP Mode) unresponsive after random amount of time, regardless of usage
2023-04-01 03:58:41 - last edited 2023-04-06 16:01:37

  @Kevin_Z I am not sure whether you guys are still producing the AX21 (Also known as the AX1800 from the Web UI and AX20 from the UART log) but I found the issue, it is indeed an issue with the thermals specifically the BCM53134, the ethernet switch chip. In order to remedy this issue, I just put a heatsink on the chip that is a bit larger than the surface area of the chip itself (I can attach a picture later if needed). If this is not already fixed in later hardware revisions, I would recommend you pass this on to the team that designs the routers. If you want to know how to reproduce this consistently, I have found running 2 speedtests via speedtest-cli on 2 seperate machines on different lan ports heats the chip up fairly quickly, after around 10-20 minutes, the router will shut itself off (likely to save the chip from getting damaged) and after adding the heatsink (and puttting the top cover on), the router seems to manage fine without crashing. Just to be safe though, I will be slamming the router for 7 days (via the above method) to see if it needs a fan (it likely wouldn't, maybe just a bigger heatsink (I'm sure for this router and maybe all of your routers, you prefer a passive cooling design) but I don't have a bigger one and I do have a 120mm fan so that will be my remedy) or if there are any other issues.

Edit: The heatsink seemed to prolong the locking so not sure if that was the issue, maybe just one of many or it wasn't the issue or needed a bigger heatsink.

Edit 2: unfortunately with such an experience, I am going to get a router that is not Broadcom based (and probably not TP-Link either) as that limits and in some cases completely shuts down custom firmware ability (in case this crash was related to firmware and not hardware)

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