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Trouble with stackwise on 3850


Hello and sorry for my bad english

We have 2 3850 Cisco Switchs. This switches are connected by stackwise by fiber link.

Problem  : sometimes, one of the 2 switch go out of the stack, not always the same, we need to reboot the switch. We don't understand because the link use by FAST HELLO is UP. Nothing in logs !

So my first question is : 
It is possible to add second link for FAST HELLO, we have first link with command "stackwise-virtual dual-active-detection", it is possible to add second fiber link between the 2 switches and add again "stackwise-virtual dual-active-detection" on this link ?
If we do that, we need to do something before pass the command ? no effect ? when we add second link, the first will not brake ?

And second question :
How analyse when the switch go out of the stack, which command ?

Thanks a lot


The configuration of the stack :

domain 1
ip routing

interface TenGigabitEthernet1/0/1
stackwise-virtual link 1

interface TenGigabitEthernet1/0/48
stackwise-virtual link 1

interface TenGigabitEthernet2/0/1
stackwise-virtual link 1

interface TenGigabitEthernet2/0/48
stackwise-virtual link 1

interface TenGigabitEthernet1/0/47
stackwise-virtual dual-active-detection

interface TenGigabitEthernet2/0/47
stackwise-virtual dual-active-detection

4 Replies 4

Kasun Bandara
VIP Advisor VIP Advisor
VIP Advisor

1. yse you can have 2 DAD links

2. to check stackwise virtual use # show stackwise-virtual

Please rate this and mark as solution/answer, if this resolved your issue
Good luck

I can just add new fiber and pass command "stackwise-virtual dual-active-detection" on the 2 switchs, no effects on existing fast hello ?

yes you can. but recommend to do it on out of office time

Please rate this and mark as solution/answer, if this resolved your issue
Good luck


we configured the new fast hello port (ports are still shutdown) and we have this warning :

WARNING: All the extraneous configurations will be removed for TenGigabitEthernet1/0/43 on reboot.
This warning is normal like is see on internet but it is not clear. We must reload or not for the new fast hello work ?
OK all extraneous will be removed, ok for me, but in can UP without reboot fast hello ports or not ?
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