Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

3750 stack problem


I have a stack of 2 x 3750's (1= master, 2= member).

Both have 2 stack cables attached. I added a third 3750 and unplugged one of the stack cables from switch 2 to and connected to switch 3. So my cabling was 1 - 2 and 1 - 3.

I hadn't added the 'switch stack-member-number priority' command to the new switch as I was planning on doing it later but thought I'd hook it up in the mean time.

This seemed to cause a problem with my master switch which went offline as if it had detatched itself for the stack and switch 2 became the master.

Removing the new switch and reloading seemed to rectify this. However I wouldn't expect adding a dormant switch to do this? Can anyone advise me on why this may have happened.


J Mack

New Member

Re: 3750 stack problem


Can anyone offer any advice on this?

Many Thanks

J Mack.

Re: 3750 stack problem

1-9 is the number of switches you can have in the stack. The priority levels are 1 - 15 with 15 being the highest and it will become master, however only on bootup the master is chosen. As your existing switch was on it's own it will be the master anyway when you add the 2nd switch. To code it to always be the master (in the event of a switch reload for whatever reason), once the new switch is in enter the command "switch 1 priority 15" , you can verify the priority settings using the show switch command. You should be able to preped the new switch by setting priority to higher so it doesnt become the new master

Tips to Add a Switch as a Slave to the Stack

To add a switch, as a slave, to a stack, complete these steps:

Note: Make sure the switch that you add into the stack has the same IOS version as the switches in the stack. Refer to Catalyst 3750 Software Upgrade in a Stack Configuration with Use of the Command-Line Interface to upgrade the IOS in a catalyst 3750 switch.

1, Change the switch priority of the switch to be added to "1".

switch stack-member-number priority new-priority-value

Note: This step is optional, but it will make sure that the switch has fewer chances to become a stackmaster in the future.

2, Power off the switch that is to be added.

3, Make sure that the stack is fully connected so that, when you connect the new switch, the stack will be at least in half connectivity and does not partition.

4, Connect the new switch to the stack with the StackWise ports.

5, Power on the newly added switch.

6, After the new switch comes up, issue the command show switch to verify stack membership.

see this for more information

pls rate