Problem with stack member priorities

[jakob.a.stevens92]

Hello, 

I am having a problem with a stack of four 2960x switches.

Before stacking the switches, I assigned them each a priority (15, 14, 13, and 12) based on the order in which they are racked. 

I stacked them together, the stack reloaded, and yet the members did not take on the switch numbers I would have expected. I reloaded the stack again, thinking perhaps the re-election had not taken place, but this did not solve the problem. 

show switch looks like this....

Switch#     Role          Mac Address        Priority     Version     State     

*1              Master      5............                15             4              Ready

*2              Member    0............                12             4              Ready

*3              Member    1............                14             4              Ready

*4              Member    0............                13             4              Ready

My understanding is that setting the priority supersedes all other factors that decide stack member elections. If that is the case, how is it that the switch with a priority of 14 is not Switch#2, the switch with priority of 13 is not Switch#3, and the switch with priority of 12 is not Switch#4 ?? 

Are there other factors that override manually-specified priority? Your advice is much appreciated. 

[Leo Laohoo]

Firstly, no one can set the priority on a switch member if the switch member is not yet on-line (meaning connected and successfully joined the stack).

So this means the stack members are in this order possibly because stack members may have already have been "numbered" before joining the stack?

[Paul Chapman · Accepted solution]

Hi -

Switches are numbered when they join the stack initially.  Once the switch is joined it's switch number is maintained through reboots by mechanisms that were hidden by Cisco.

The priority is used for stack elections as to who will be the stack master.

Since your stack is already built, you will need to reboot a few times to get everything where you want it.

(config)# switch 2 renumber 5
(config)# end
(config)# copy run start
(config)# reload

Run through the process to change 3 to 2, then 4 to 3, then 5 to 4.  Check individual port configs when complete.

My team put together a few hundred 2960x stacks for a single project.  We used the following procedure to ensure that switches joined in the proper order:

1. Boot first switch with no stack cables installed (cuts down boot time by skipping stack election)
2. Once first switch is booted install all stack cables
3. Boot second switch (Switch 1 is already master so stack election is fast)
4. Boot addition stack members at 15-30 second increments from previous (i.e. switch 3 thirty seconds after switch 2, then switch 4 thirty seconds after switch 3) (this ensures desired switch numbering)
5. Apply switch priorities
6. Apply stack baseline config
7. Save config and rebox

Good Luck!

PSC

[jakob.a.stevens92]

Hi Leo, 

Actually, at least in the case of 2960x, each individual switch considers itself a stack of one, and so a priority can be set on an un-stacked individual switch by using 

(config)# switch 1 priority ___

Supposedly, when the switches are stacked, these priorities are retained by the members and the stack numbers itself according to administrator design ---- but it does not seem to be the case 100% of the time, as I am finding out with this particular scenario.