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cat3750 stack, sw-upgrade without rebooting the whole stack at the same tim

Unanswered Question
May 5th, 2006
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i've gout a question regarding catalyst 3750 stack software upgrades.

is there any possibility to do a software upgrade to the stack without rebooting all stack

members at the same time?

i tried to do this manually with "archive download-sw /overwrite"

(without using /force-reload or /reload parameters) and then reboot one of the two members

in the stack. the remaining switch correctly becomes the Master. But when the member with the

new software comes up again, a version missmatch is detected (by the switch running the old sowftware) and the upcomming switch stucks in the boot process.

so everything i tried, i've got a network down for the whole stack.

we have a scenario where servers are connected to both members of a stack (for REDUNDANCY and

bandwidth aggregation). it would be nice if' there's any procedure to do an upgrade in the stack without

losing both connections to our servers at the same time...

kind regards

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brian.kennedy Fri, 05/05/2006 - 05:24
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I'm pretty sure this is not possible. I posted on this about 6 months ago (the exact same reason - servers dual connected to our stacked 3750's). But you're correct; once you upload the software and reload one, you'll have a sw version mismatch. If you bring a new switch into the stack that has older sw, the new software will be pushed down to it, but it doesn't help with existing.

mogli Mon, 05/08/2006 - 04:22
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hi clare,

thanks for your reply. i tried your described procedure, but with no success.

rebooting both switches, regardless which software the have in their flash, will interrupt the connected servers, because both links (to the stack) are going down at the same time (to achieve this, its easier to use the standard procedure as described in the config guide).

the idea with a seperated sw-download with different feature-set's sounded interesting for me in the first moment.

unfortunately it doesn't work too. after the sepedated download to the switches as soon as i reboot one the switches to load the new software, the other becomes (or stays) master of the stack. once the rebooted switch with the new software comes up again, the mastes displays a version mismatch (and the upcoming switch stucks in operation, awaiting the pretended correct software).

at this stage i can only reboot the master switch which results in complete outage of the stack (the upcoming stucking switch reboots too).

i have posted the question in the "ask the expert, high availability.." threat too, so maybe the expert has an idea to accompish this task ;-)

kind regards

dasberry Mon, 05/08/2006 - 06:09
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Yes. this is accomplished through the Stack Master. Once you have upgraded the Master and perform a reboot the election process will be redone. Don't fret with a software mismatch.

AS long as you upgrade the master first, you can do individual devices within the stack. Go to this URL, to see how this is performed:



mogli Mon, 05/08/2006 - 07:41
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i'm not sure that i understand what you are trying to describe me. also if i upgrade the master first, there is an outage of both switches at the same time.

in the meantime Bobby from Cisco gave an answer to this topic in the "ask the expert" threat. you can find it following this link:


maybe a zero downtime with a 3750 stack upgrade would be a great thing for future releases.... :-)



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