Adding Catalyst 3750 to stack

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May 7th, 2009
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I have a stack of Catalyst 3750. I want to add another Catalyst 3750 (Same IOS) to the stack. when I connect the switch to the stack, will this interrup the current users connected to the stack? Is there any steps I need to do before connecting the switch to the stack?

Thanks in advance.

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Giuseppe Larosa Thu, 05/07/2009 - 04:27
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Hello Serge,

you can use the following document as a reference

I would do it during a maintanance window.

There is the possibility to provision the new switch and you need also to use priorities to be sure of what switch is the master in the stack.

Hope to help


Jason Fraioli Thu, 05/07/2009 - 05:12
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I added a 3750 to a stack yesterday. If your existing 3750 hasn't had any "switch" priority commands entered, it will become the master. You'll need to make sure that the existing switch gets the stack cable connected to port 1, and port 2 on the new 3750. I didn't notice any downtime, but as always, I would suggest doing it during it after hours.

You will have to go in and set specific port commands, such as cdp, portfast, vlan, switchport modes, etc.

I think the master is supposed to copy its IOS image over to the new member if the member does not have the correct IOS. I have not tried it that way though. I always make sure the new member has the correct image ahead of time.

On the primary switch do the following:

Switch(config)#switch 1 priority 15

Switch(config)#switch 1 provision

Switch#show switch

Switch/Stack Mac Address : 0019.0680.e980

H/W Current

Switch# Role Mac Address Priority Version State


*1 Master 0019.0680.e980 15 0 Ready

That will make sure the current master is prepared.

To add the second switch to the stack:

Switch(config)#switch 2 provision

You may now configure all the ports for the new switch.

Rack the new switch, connect the stacking cables, and power on.

You can optionally set second switch priority for failover once it is on and powered on.

Switch(config)#switch 2 priority 14




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