RT-AX86U - Crashing/Rebooting and ISP does not function properly

[Rassal]

Hi All...

I am getting every couple of days, a crash which the router reboots completly, and sometime connects fine, sometime i get the dreaded ISP DHCP doesn't work properly message... which i can live with.

The problem i am facing, is WHY it is crashing... and i tried to see why, and can't find it. I need some help/guideline on what could be causing this.

I got an RT-AX86U that i bought brand new at Black Friday last year (Nov 2020), as soon as i saw it was Merlin supported, that's why i bought it.

It works well, and i purchased this to replace an old RT-AC87U, which i was using for like 5 years.

I did flash a few Beta build and it was working fine with the betas, but i was never getting more than a couple of days under the betas, of stability, because they were beta versions, and also because there was new beta that i flashed when they were available.

Then came the final version, and since the final version, it remained unflashed for days/weeks now, and using 386.1_2 now for a few weeks.

When the final version came, i did the whole factory reset, and configured it all manually from scratch, and it's fine. Beside the fact that it crash sometimes, and reboot, and i can't find why...

Today, i got one of those crash, and grabbed the log from 1PM up to almost now, which shows the crash at around 14h50, then the reboot, and the WAN that connects back...

I am using AMTM, along with SkyNet, FlexQoS, Scribe, nsrum, Connmon, SpdMerlin uiScribe and of course, Entware. So far, everything is ok... the only thing i can see, is that some of my Wifi PC at home, are getting generating DHCPDECLINE for some unknown reason, and don't grab their IP that i set on the DHCP reservation list... and i don't know if those DHCPDECLINE could be the cause of the crashes.

Nobody complains in the house about Wifi Dropping, me neither. I am using 2.4 and 5Ghz combined as a single SSID and using 160mhz because i do not have any weather radar close to me, and 5ghz 160mhz works fine along with all AX client using 160mhz. No problem there.

Just the problem that the router crashes, reboot, and of course, when this happen, everyone comes running to me saying the Internet doesn't work... and usualy the router reboots by itself and it's fine, unless i get the dreaded ISP DHCP not working properly, then i need to reboot a couple of times to get it to work...

I attached the log of today, showing about 3h of activitity, and the crash... anyone more knowledgeable than i am to take a look and give me a hint on what could cause the crash?

I see a lot of CRASH logs in there, but they really don't speak to me...

SO i have no idea where to start from...

 

[jpthsd]

Hi All...

I am getting every couple of days, a crash which the router reboots completly, and sometime connects fine, sometime i get the dreaded ISP DHCP doesn't work properly message... which i can live with.

The problem i am facing, is WHY it is crashing... and i tried to see why, and can't find it. I need some help/guideline on what could be causing this.

I got an RT-AX86U that i bought brand new at Black Friday last year (Nov 2020), as soon as i saw it was Merlin supported, that's why i bought it.

It works well, and i purchased this to replace an old RT-AC87U, which i was using for like 5 years.

I did flash a few Beta build and it was working fine with the betas, but i was never getting more than a couple of days under the betas, of stability, because they were beta versions, and also because there was new beta that i flashed when they were available.

Then came the final version, and since the final version, it remained unflashed for days/weeks now, and using 386.1_2 now for a few weeks.

When the final version came, i did the whole factory reset, and configured it all manually from scratch, and it's fine. Beside the fact that it crash sometimes, and reboot, and i can't find why...

Today, i got one of those crash, and grabbed the log from 1PM up to almost now, which shows the crash at around 14h50, then the reboot, and the WAN that connects back...

I am using AMTM, along with SkyNet, FlexQoS, Scribe, nsrum, Connmon, SpdMerlin uiScribe and of course, Entware. So far, everything is ok... the only thing i can see, is that some of my Wifi PC at home, are getting generating DHCPDECLINE for some unknown reason, and don't grab their IP that i set on the DHCP reservation list... and i don't know if those DHCPDECLINE could be the cause of the crashes.

Nobody complains in the house about Wifi Dropping, me neither. I am using 2.4 and 5Ghz combined as a single SSID and using 160mhz because i do not have any weather radar close to me, and 5ghz 160mhz works fine along with all AX client using 160mhz. No problem there.

Just the problem that the router crashes, reboot, and of course, when this happen, everyone comes running to me saying the Internet doesn't work... and usualy the router reboots by itself and it's fine, unless i get the dreaded ISP DHCP not working properly, then i need to reboot a couple of times to get it to work...

I attached the log of today, showing about 3h of activitity, and the crash... anyone more knowledgeable than i am to take a look and give me a hint on what could cause the crash?

I see a lot of CRASH logs in there, but they really don't speak to me...

SO i have no idea where to start from...

was it very quick crash/reset? like your computer didn't notice it so the connection adapter in the bottom right corner didn't change to no Internet at all? even some WiFi client watching youtube didn't even notice or get interruption?

While my AX86U on 386.1, it rebooted/reset itself very very quick like a soft-reset/soft-reboot 90s and router was back online again!! I watched it by my own, my computer network adapter's connection status didn't get change to No Internet, my wifi phone was playing youtube didn't even get disconnected nor interruption as it happened like 1-2 minute reset/reboot... very very fast. The strange thing like yours, I could not find it in the log!

 

[Rassal]

Yes, it was pretty quick, but i never know if i will get the ISP DHCP not functioning properly... so i had to watch it reboot... and light came back pretty quick... nobody came rushing for me ;-)

But i did lost a few connections i had, but it lasted maybe 2-3 min at max, between the time i found out the router was rebooting, and when the WAN reconnected... I didn't had time to check if i lost the adapter to "no internet". But i was using an RDP connection, and was faced with the 1 of 20 retry to connect... but it dropped, because it was too long for the RDP to resume...

Very quick, but still... it crashed... and i am trying to understand why...

 

[Rassal]

And i can see in the LOG that it reboots, because the logs have the date/time stamp, until the crash, where it reverts to like May 5... then when WAN reconnects and NTP kicks in, the logs are getting back insync with time and date... so i can only see the reboot period because it was logged as May 5...

But then during that time, i see a lot of CRASH: log entries, which i have no idea what they refer to... which is what i am trying to understand.

 

[Rassal]

In my logfile i provided on the first post in the thread, i was able to extract the crashlog, and it looks like this, twice:

Line 633: May 5 01:05:10 crashlog: <0>Internal error: : 8a000000 [#1] PREEMPT SMP
Line 634: May 5 01:05:10 crashlog: <4>CPU: 0 PID: 258 Comm: bcmsw_rx Tainted: P O 4.1.52 #2
Line 635: May 5 01:05:10 crashlog: <4>Hardware name: Broadcom-v8A (DT)
Line 636: May 5 01:05:10 crashlog: <4>task: ffffffc03dc14b40 ti: ffffffc030794000 task.ti: ffffffc030794000
Line 637: May 5 01:05:10 crashlog: <4>PC is at 0x3f8b0728244b9
Line 638: May 5 01:05:10 crashlog: <4>LR is at 0xb203f8b0728244b9
Line 639: May 5 01:05:10 crashlog: <4>pc : [<0003f8b0728244b9>] lr : [<b203f8b0728244b9>] pstate: 00000145
Line 640: May 5 01:05:10 crashlog: <4>sp : ffffffc030797570
Line 641: May 5 01:05:10 crashlog: <4>x29: d8283ab8f504b896 x28: ffffffc02bb6f2d0
Line 642: May 5 01:05:10 crashlog: <4>x27: ffffffc0307977d0 x26: 0000000000000000
Line 643: May 5 01:05:10 crashlog: <4>x25: ffffffbffc366a28 x24: 00000000005400b9
Line 644: May 5 01:05:10 crashlog: <4>x23: ffffffc030797638 x22: 4f923e5290981c0c
Line 645: May 5 01:05:10 crashlog: <4>x21: 4610be8481a14e22 x20: 345c64a92c6b0343
Line 646: May 5 01:05:10 crashlog: <4>x19: 980cbaeb7caa421d x18: 00000000aafe337a
Line 647: May 5 01:05:10 crashlog: <4>x17: 00000000005ecc4d x16: 000000000000000d
Line 648: May 5 01:05:10 crashlog: <4>x15: 0000000000000008 x14: 00000000aafe3373
Line 649: May 5 01:05:10 crashlog: <4>x13: 0000000000000014 x12: 00000000ffffffff
Line 650: May 5 01:05:10 crashlog: <4>x11: ffffff80094ce000 x10: 0000000000000000
Line 651: May 5 01:05:10 crashlog: <4>x9 : 0000000000000049 x8 : 0000000000000000
Line 652: May 5 01:05:10 crashlog: <4>x7 : 0000000049000001 x6 : 00000000ffffffff
Line 653: May 5 01:05:10 crashlog: <4>x5 : 0000000000000010 x4 : 0000000000000010
Line 654: May 5 01:05:10 crashlog: <4>x3 : 000000000000373d x2 : ffffffc030794000
Line 655: May 5 01:05:10 crashlog: <4>x1 : 0000000000000401 x0 : 0000000000000002

Then a little later:

Line 828: May 5 01:05:10 crashlog: <0>Call trace:
Line 829: May 5 01:05:10 crashlog: <0>Code: bad PC value
Line 830: May 5 01:05:10 crashlog: <4>---[ end trace 24643c3b5902e75a ]---
Line 831: May 5 01:05:10 crashlog: <0>Kernel panic - not syncing: Fatal exception in interrupt
Line 832: May 5 01:05:10 crashlog: <2>CPU3: stopping
Line 833: May 5 01:05:10 crashlog: <4>CPU: 3 PID: 0 Comm: swapper/3 Tainted: P D O 4.1.52 #2
Line 834: May 5 01:05:10 crashlog: <4>Hardware name: Broadcom-v8A (DT)
Line 835: May 5 01:05:10 crashlog: <0>Call trace:
Line 836: May 5 01:05:10 crashlog: <4>[<ffffffc000087398>] dump_backtrace+0x0/0x150
Line 837: May 5 01:05:10 crashlog: <4>[<ffffffc0000874fc>] show_stack+0x14/0x20
Line 838: May 5 01:05:10 crashlog: <4>[<ffffffc00054dce8>] dump_stack+0x90/0xb0
Line 839: May 5 01:05:10 crashlog: <4>[<ffffffc00008d710>] handle_IPI+0x190/0x1a0
Line 840: May 5 01:05:10 crashlog: <4>[<ffffffc000080c68>] gic_handle_irq+0x88/0x90
Line 841: May 5 01:05:10 crashlog: <4>Exception stack(0xffffffc03e8d7dc0 to 0xffffffc03e8d7ef0)

So obviously, there was a real crash, which is why it rebooted... but this doesn't speak to me at all...

I attached the crashlog portion of my log i provided at first...

 

[Rassal]

was it very quick crash/reset? like your computer didn't notice it so the connection adapter in the bottom right corner didn't change to no Internet at all? even some WiFi client watching youtube didn't even notice or get interruption?

While my AX86U on 386.1, it rebooted/reset itself very very quick like a soft-reset/soft-reboot 90s and router was back online again!! I watched it by my own, my computer network adapter's connection status didn't get change to No Internet, my wifi phone was playing youtube didn't even get disconnected nor interruption as it happened like 1-2 minute reset/reboot... very very fast. The strange thing like yours, I could not find it in the log!

Well, it crashed again tonight... since last time, it's the only crash, but this time, it did exactly the same as it did to you, very fast reboot/reconnect, some people were looking at YouTube and didn't even notice the reboot of the router. I did not get the "no internet" globe on the adapter... so it seems to be somewhat very likely as you described it.

This time, this is what i had in the log when it rebooted in the crashlog...

Line 617: May 5 01:05:08 crashlog: <0>Code: bad PC value
Line 618: May 5 01:05:08 crashlog: <0>Internal error: Oops: 96000005 [#2] PREEMPT SMP
Line 619: May 5 01:05:08 crashlog: <4>---[ end trace 5838721ba0ecbc77 ]---
Line 620: May 5 01:05:08 crashlog: <0>Kernel panic - not syncing: Fatal exception in interrupt
Line 621: May 5 01:05:08 crashlog: <2>CPU2: stopping
Line 622: May 5 01:05:08 crashlog: <4>CPU: 2 PID: 0 Comm: swapper/2 Tainted: P D O 4.1.52 #2
Line 623: May 5 01:05:08 crashlog: <4>Hardware name: Broadcom-v8A (DT)
Line 624: May 5 01:05:08 crashlog: <0>Call trace:
Line 625: May 5 01:05:08 crashlog: <4>[<ffffffc000087398>] dump_backtrace+0x0/0x150
Line 626: May 5 01:05:08 crashlog: <4>[<ffffffc0000874fc>] show_stack+0x14/0x20
Line 627: May 5 01:05:08 crashlog: <4>[<ffffffc00054dce8>] dump_stack+0x90/0xb0
Line 628: May 5 01:05:08 crashlog: <4>[<ffffffc00008d710>] handle_IPI+0x190/0x1a0
Line 629: May 5 01:05:08 crashlog: <4>[<ffffffc000080c68>] gic_handle_irq+0x88/0x90
Line 630: May 5 01:05:08 crashlog: <4>Exception stack(0xffffffc03e8cfdc0 to 0xffffffc03e8cfef0)
Line 631: May 5 01:05:08 crashlog: <4>fdc0: 877b652c 00006682 00000000 00000080 3e8cff10 ffffffc0 0038159c ffffffc0
Line 632: May 5 01:05:08 crashlog: <4>fde0: 877b652c 00006682 ccfa4bf2 00273c2f 00013e3a 00000000 14000a95 00000000
Line 633: May 5 01:05:08 crashlog: <4>fe00: 0bdfa866 00000000 00000018 00000000 37d2d030 00272353 32aa1628 ffffffc0
Line 634: May 5 01:05:08 crashlog: <4>fe20: 3e8c3a70 ffffffc0 3e8cfec0 ffffffc0 f7391000 00000000 00000000 00000000
Line 635: May 5 01:05:08 crashlog: <4>fe40: ff892154 00000000 ff892168 00000000 f738a970 00000000 00000000 00000000
Line 636: May 5 01:05:08 crashlog: <4>fe60: 000f5a28 ffffffc0 00000000 00000000 00000000 00000000 877b652c 00006682
Line 637: May 5 01:05:08 crashlog: <4>fe80: 3ffd4338 ffffffc0 00000001 00000000 00000001 00000000 8778f1e7 00006682
Line 638: May 5 01:05:08 crashlog: <4>fea0: 3e8cc000 ffffffc0 00908000 ffffffc0 00736000 ffffffc0 3ffd4338 ffffffc0
Line 639: May 5 01:05:08 crashlog: <4>fec0: 007790b8 ffffffc0 3e8cff10 ffffffc0 00381594 ffffffc0 3e8cff10 ffffffc0
Line 640: May 5 01:05:08 crashlog: <4>fee0: 0038159c ffffffc0 60000145 00000000

So it was again a Fatal exception in interrupt...

No idea why it does it...

 

[KevTech]

I am using AMTM, along with SkyNet, FlexQoS, Scribe, nsrum, Connmon, SpdMerlin uiScribe and of course, Entware.

First step in troubleshooting is to start with an overall stock firmware install even on Merlin.
Perhaps to troubleshoot your issue you remove all of these add-ons and see if the crashes stop.
If the crashes do stop then start adding things in one at a time with a day or two in-between installs until you see which one is crashing the router.