[c-nsp] 3750 stack

Alan Buxey A.L.M.Buxey at lboro.ac.uk
Wed Aug 25 18:01:10 EDT 2010

> One of potential problem to have only one single stack is the downtime
> during OS upgrade (and other maintenance).
> Two stack and backup each other via VRRP/HSRP could provide higher
> availability to clients (machines/customers) under them, provided those
> clients equips two up links to two different stacks.

yes, I was going to ask about this - there isnt a direct way that I can see
from cisco docs to upgrade a stack without suffering downtimes...thus all hosts
connected.  I can see a way of doing it that might work (havent tested
the theory yet) if the hosts or switches connected are dual-linked
or more to the stack.

1) force software upload onto a member, reboot said member... 
2) stack will either migrate to new member when it reloads with latest
IOS or mark it as version mismatch and not put it into operation - now
reload other member(s) - the newest upgrade may now come into play
3) upgrade other members....then reload them.

hmm. any real or recommended ways?  these stacks are supposed to
remove SPoF location but at some point we need to reload (just like
our routers - but those can be - as the aggregation switches are linked
to multiple routers and we use eg HSRPv2 et al.. in fact, currently we can
drop 50% of our routers during working hours without end user
(thats great, it means less working strange hours) - but now our
aggregation layer is the pain......


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