No, you need not have to TURN OFF the existing switch while adding a new switch in STACK, cisco 3750 stacking technology has been designed in such a way that when ever you connected a new switch in the stack, it automatically upgrades the IOS to the newly stacked switch. also you don't require any downtime for that new switch, it alone gets rebooted once the IOS is upgraded. you need not bother about the existing switches which is up & running.

hope your are clear.

rate this post if your satisfied.

hey experts

what i mean is because switch1 and switch2 is connected together in their stack1 and stack2 ports, is it safe to unplug the stack cable from switch1 and switch2 while it's power on?

check this link http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml#stack2 and see item 1 where two switch stack ports are connected together can i just remove one of the stack cable while the two switch is power on and insert two power off new slave switch, connect the stack cable accordingly like shown in item 4? won't it create problem on the stack ports of switch1 and switch2?

thank you experts, ya all vry helpful

things looks so simple but could be dangerous. i just wonder why cisco didn't mention that in the doc, its like leaving it blur if something screw up can just say "i didn't specifically mentioned that didn't i" :0