3850 Stack mode

[TF.DE]

Hi,

on a running projekt I took over some 3850 stacks.
The stacks are configured with two 3850 devices.
I check the redundandy configuration and see, that they are configured with default N+1 stack mode.
What is your recommendation, configure the two devices in 1:1 stack mode or leave it at default
with N+1.

Regards

[balaji.bandi]

If this 2 switches does not matter 1:1 or n+1 , since only 1 can become master and another one as slace or standby, if you have more than 2 switches in stack, it matter, because you like only fist 2 switches to be master or slave, since uplinks connected to those switches as per major designs.

But suggestion is make sure you define with priorities, so one should become master always when the switch reloads.

some reference :

1:1 redundancy is used to assign active and standby roles to specific switches in the stack. This overrides the traditional N+1 role selection algorithm, where any switch in the stack can be active or standby. In 1:1 redundancy, the stack manager determines the active and standby role for a specific switch, based on the flash ROMMON variable. The algorithm assigns one switch as active, another switch as standby, designating all remaining switches in the stack as members. When an active switch reboots it becomes standby and the existing standby switch will become active.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-6/configuration_guide/b_166_stck_mgr_ha_3850/b_166_stck_mgr_ha_3850_chapter_011.html

[TF.DE]

Thanks for the response. 

Last time, when I reboot the stack, one of the stack member come back as member not as standby.

So, I changed from n+1 to 1:1, after the next reboot the two devices come back als primary and standby.

Then I was not sure, that the default with n+1 is the best configuration.

[balaji.bandi]

yes setting config is gives confidence they become master or standby, as precaution i would do that..