Re: Anyone else seen this. [Draytek rebooting]

In uk.d-i-y jkn <[email protected]> wrote:
> On 03/07/2026 22:16, The Natural Philosopher wrote:
> > On 03/07/2026 16:45, jkn wrote:
> >> On 03/07/2026 16:21, The Natural Philosopher wrote:
> >>> Recently my router (Draytek 2726) has been spontaneously rebooting.
> >>>
> >>> Examination of the logs show a kernel panic caused by 'attempt to 
> >>> execute an illegal instruction'.
> >>>
> >>> My assumption, possibly erroneous, is that the actual firmware code 
> >>> is corrupted
> >>> The router is rated only to +45°C but that is the recommended limit 
> >>> for flash memory, and the room temperature has been up towards 40°C. 
> >>> which doesn't leave a great deal of margin for router internal heat 
> >>> production.
> >>> My query is whether anyone else has seen issues with flash memory in 
> >>> the recent hear wave.
> >>>
> >>> Surely phones get hotter than this?
> >>>
> >>> Genuinely interested in other's experiences.
> >>>
> >>
> >> I have a Draytek 2927 series - it is not new to me, but was previously 
> >> used in a commercial environment with no issues AFAIK.
> >>
> >> I have noticed a situation with mine where the connection both wired 
> >> and wireless) appears to drop momentarily, on occasion (couple of 
> >> times a week?)
> >>
> >> I recently looked at the log, and saw something similar to what you 
> >> describe - the router was in fact rebooting, and the log shows 
> >> something like:
> >>
> >>  > sys ver dbg
> >>
> >> Router Model: Vigor2927ax    Version: 4.5.2 English
> >> Profile version: 4.0.0    Status: 1 (0x9de71d0f)
> >> Router IP: 192.168.0.1    Netmask: 255.255.255.0
> >> Firmware Build Date/Time: Feb 12 2026 17:45:01
> >> Router Name: DrayTek
> >> Revision: 6562_fd593bfca2 drayos2015
> >> Router serial no: None
> >>
> >> ---------firmware exception debug info on 
> >> cpu0-----------------------------
> >>
> >> # etc.
> >>
> > Yes. that is significant. Its the next bit of the log before the 
> > registers dump that is significant
> > 
> > Mine said (in shorthand) 'The CPU tried to execute an instruction that 
> > does not exist'
> > 
> 
> Yes, my log has:
> 
> ---------firmware exception debug info on cpu0-----------------------------
>   EPC=60034b60, Cause=00800014, Status=1100fc03, BadAddr=00000000, 
> RetAddr=60034a58
>   exception id=5(ADES: Address Error Store)
>   exception occured in TASK Level
>   task_id=161, SP=0x629390b8(3188 bytes free, 5664 used bytes)
>   system tick =26381273
>   CURRENT_VERSION : 4.5.2_RC5
>   get from address : 60017000
>   Dump CPU0 registers:
> ...
> 
> 
> but if you look eg. here:
> 
> https://www.draytek.co.uk/support/guides/kb-troubleshoot-reboot
> 
> they list a log like this - this seems a 'normal' feature of reboot 
> issues, without considering flash failure.

That looks like MIPS. The Cause register bits 2-6 gives you the type of
exception. For yours:

Cause[6:2] = 5 which means 'Store to illegal address'

TNP's has:

Cause[6:2] = 10 which means 'Reserved instruction'

codes from:
http://www.cs.iit.edu/~virgil/cs470/Labs/Lab7.pdf

They are different types of exception, even if the information is presented
in the same way.

Theo