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New Member

stacking 3750 g


I was wondering I f I am adding a new switch to the stack will it cause any intruptions during the cable changes? Also Is it ok to change the stack number of the switch in production env. will it retain the Vlan assignment or config?

Thanks in advance



Re: stacking 3750 g

A switch stack has up to nine stack members connected through their StackWise ports. A switch stack always has one stack master.

A standalone switch is a switch stack with one stack member that also operates as the stack master. You can connect one standalone switch to another (Figure 5-1) to create a switch stack containing two stack members, with one of them being the stack master. You can connect standalone switches to an existing switch stack (Figure 5-2) to increase the stack membership.

If you replace a stack member with an identical model, the new switch functions with exactly the same configuration as the replaced switch, assuming that the new switch is using the same member number as the replaced switch. The specific procedure for replacing a failed switch is described in the "Troubleshooting" chapter in the hardware installation guide.

The operation of the switch stack continues uninterrupted during membership changes unless you remove the stack master or you add powered-on standalone switches or switch stacks.



Make sure the switches that you add to or remove from the switch stack are powered off.

After adding or removing stack members, make sure that the switch stack is operating at full bandwidth (32 Gbps). Press the Mode button on a stack member until the Stack mode LED is on. The last two port LEDs on all switches in the stack should be green. Depending on the switch model, the last two ports are either 10/100/1000 ports or small form-factor pluggable (SFP) module ports. If, on any of the switches, one or both of the last two port LEDs are not green, the stack is not operating at full bandwidth.


Adding powered-on switches (merging) causes the stack masters of the merging switch stacks to elect a stack master from among themselves. The re-elected stack master retains its role and configuration and so do its stack members. All remaining switches, including the former stack masters, reload and join the switch stack as stack members. They change their stack member numbers to the lowest available numbers and use the stack configuration of the re-elected stack master.

Removing powered-on stack members causes the switch stack to divide (partition) into two or more switch stacks, each with the same configuration. This can cause an IP address configuration conflict in your network. If you want the switch stacks to remain separate, change the IP address or addresses of the newly created switch stacks. If you did not intend to partition the switch stack:

a. Power off the newly created switch stacks.

b. Reconnect them to the original switch stack through their StackWise ports.

c. Power on the switches.

For more details see:


If this helps, please rate

New Member

Re: stacking 3750 g


Thanks for the reply but my question is has anyone done this and does it cause any problems. Also I want to change the member no of the swith to another one. Will the switch I say show up as 4/0/34 int if I change member 4 to 5 will it show up as 5/0/34 and retain the config for the int.


Re: stacking 3750 g

Been there got (part) of the T-shirt

Adding switch in running stack: no problem.

For me it is common practise to add an (of power) switch to a stack. That will be added without the rest of the stack falling down. They stay up and running and there is no network dip while adding the new switch.

Config on stackmember:

When a 3750 switch is added to a 3750 stack, It will receive its memberstacknumber and its runningconfig wil be synched with the running config on the master switch. So if you take the switch out of the stack, it will have the running config. Therefore, if you renumber the switches, the config for switches will be alike, but I can't tell if the interfaces are reconfigured aswel. (lets say, 1/0/1 is a voiop port and has a different setting as 2/0/1 (trunk port). If you change membernumbers (en 1/0/1 will become 2/0/1 logicly), will the configuration parameters of 1/0/1 be renumbererd to 2/0/1? I really don't know..

It is worth a try.. I will look tuesday if we have two extra spare 3750 and try this one out as I myself want to know now aswell.

Will respond on tuesday with hopefully the definitive answer.

(If this helps, please rate)

New Member

Re: stacking 3750 g

I had a 4 switch stack and added 2 more switches to it it, in the middle of the day, and it did not cause any interruptions. I just had to make sure that the switches i was putting into the stack had the exact same IOS as what was already there.

New Member

Re: stacking 3750 g

I've added a 3750G to the stack without any interruptions. I also preconfigured the switch stack priority before connecting the new switch into the existing stacks without any problems. On startup is when it does the stack elections. I agree with the post above, make sure the IOS versions are the same.

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