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Thiago Perrini

Downgrade WS-C3850-48P (16.x -> 3.x) BIST Fail

We are trying to perform a downgrade from IOS-XE Denali 16.3.3 to 3.6.6E but the switch allways hangs at Built-In Self Test "BIST failed. Abort init..."

All packages are Digitally Signed
Starting System Services
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=4,mode=600,ptmxmode=000 0 0
FIPS(NGWC): Flash Key Check : Begin
FIPS(NGWC): Flash Key Check : End, Not Found, FIPS Mode Not Enabled
BIST failed. Abort init ...
BIST failed. Abort init ...

We also can't boot the switch from usbflash with an 3.6x or 3.7x, with 16.x the switch boots without problem.

We also tried with the emergency-install and we had the same results.

When we boot from usb or install IOS 16.3.x the switch boots normaly.

This problem have similarities to that case:

or Bug ID's



Has anyone maybe a solution to that problem?


Reza Sharifi
Hall of Fame Expert

Not sure if it helps your case, but there was another post about this a couple of days ago.

If not, you may wan to open a case with TAC.


Leo Laohoo
VIP Community Legend

I've just stumbled upon this bug.  I think this appliance is a new "hardware version" and doesn't support any IOS versions other than 16.3.X and later.  

So there is no workaround to this issue other than to upgrade to Denali.

Leo Laohoo
VIP Community Legend

Hey Thiago, 

The Bug ID published lacked very important details to help anyone identify if their newly arrived switches are affected by the hardware/software "bug".  

May I request if ANYONE who's his this bug post the following information: 

  1. First seven (7) characters of the serial number(s); and 
  2. Exact model number of the switches. 

Thank you very much.

hy leo 

thats possible that new hardware version isn't compatible... maybe a newer hardware release. 

I wasn't able to resolve that problem. With the new IOS 16.x the switch ran always without problems. with the 3.x IOS version the switch always stuck on BIST Fail.

I resolved my problem with an RMA.  

SN: SFCW192xxxxx (BIST Fail)
MO: WS-C3850-48P-S

SN: SFCW204xxxxx (No problem to downgrade)
MO: WS-C3850-48P-S


Hey Thiago, 

You're not hitting this bug.  This doesn't make any sense.  Serial number tells me the switch was manufactured in 2015 (around May).  So it's not a new switch manufactured in 2017.  

Hey Thiago, the old appliance (I know it's already been RMA-ed) PID, was there a version number at the end?  If it does, do you remember what it was?

Thanks for the serial number and the PID.  Will help others.

I get it -- this post is OOOOOOLD....


I'm just posting a link that appears to address this process of what you do if you end up getting the BIST Init error.  For me, I substituted the bin file for v16