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3850-24XS-E Switch Stack symptom mystery. Please help?


Hello folks.

I'm investigating an incident with two 3850-24XS-E switches configured as a stack. Both switches have remained online during this incident. The #2 switch in the stack order is currently the active switch, and has been for 10 months. A week ago the #2 switch showed the symptom...

"%PLATFORM-4-ELEMENT_WARNING: Switch 2 R0/0: smand: 2/RP/0: Used Memory value 92% exceeds warning level 90%".

The symptom persisted for about a week, up to 93% used memory, then the symptom vanished- now the #2 switch memory is approximately 50% used (normal).

I do not have access to all information, such as the logs from switch#1, or what happened 10 months ago.

I have researched that, yes, there exists memory bugs within the current (same) IOS of both switches.

I have the "show tech" from switch#2.


Questions: 1. Does this default configuration incorporate preemption? (Why is the #2 switch still the master?)

                 2. If switch #1 failed in some way 10 months ago, but is now online, would this have always caused a major incident, or could there exist a scenario in which this switch failure went unnoticed by a negligent network administrator?


If you have any helpful input to this mystery, I would greatly appreciate it!


-Mic Jameson




VIP Guru VIP Guru
VIP Guru

As you mentioned you have effected with the BUG


When the 2 switches in the stack, the config is replicated master and standby automatically, so if the master switch dies, the standby switch take over the master role that is normal, when the master switch returns it will act as standby only it can not act as master here.


not sure what happened 10months too long, user device connected to switch 1 should have been lost, the user might have complained?


if you have any monitoring system it may have given logs and notification, this may have been ignored looks like.


The suggestion here is to upgrade to stable IOS both stack and reload for a stable connection.





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Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

I am still waiting for the output to the commands you've promised in your first thread.

Thank you Leo for your continued interest.


I did ask my client to input the commands your suggested. My client is not very responsive to my requests. 


I told the client that, in all cases, the correct next action was to upgrade the IOS of the switch stack.

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