Replacement of faulty switch in stack WS-C3750X-12S

[tanner.zaitt]

Hello All,

I have a question.
How could I remove the faulty switch which is member 1 from the stack (it's not the master)?
And then how can I add the new switch as member 1 from the stack?

For me is important the new switch to be replaced as member 1 from the stack, cause I have important configuration on interface range Gi1/0/X.


Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
2 18 WS-C3750X-12S 15.0(2)SE11 C3750E-UNIVERSALK9-M
3 30 WS-C3750X-24 15.0(2)SE11 C3750E-UNIVERSALK9-M
* 4 30 WS-C3750X-24 15.0(2)SE11 C3750E-UNIVERSALK9-M

Switch# Role Mac Address Priority Version State
----------------------------------------------------------
1 Member 0000.0000.0000 0 0 Provisioned
2 Member acf2.c5d5.3600 1 3 Ready
3 Member f872.ea4a.1380 1 3 Ready
*4 Master f872.ea05.dd00 1 3 Ready


For now I just did shutdown of the faulty member 1.

Could you please guide me trough the right steps to replace the faulty switch in the best possible way?
Thank you in advance.

[M02@rt37]

Hello @tanner.zaitt,

First, ensure the new switch is running the same IOS version. Also, you will need to renumber the new switch once it is in place in the stack.

-Power down switch 1 and remove the stacking cable,

-Remove switch 1,

-Install new switch,

-No Power On the new switch 

-Connect stacking cable,

-Power On the new switch.

After the faulty switch is powered down, the stack will automatically renumber the members. Member 2 might become the new member 1. Allow the stack to fully reload.

When connecting the new switch to the stack using the stacking cables and power On, it will be assigned a stack member number based on the current stack configuration.

If the new switch is not assigned as member 1, you will need to manually renumber the stack:

switch <current_member_number> renumber <new_member_number>

Apply the config that was on the interface range Gi1/0/X from the backup to the new switch's interface range.

[tanner.zaitt]

Hi, Thank you for the information.
But do you have chance to join the new switch directly as member 1 without any reloads of the stack?
Now I have 3 switches in stack and they are up and run:
switch 2, 3 and 4, the number of members are not changed.
Switch 4 is master.
I removed stack cables of the faulty switch 1.
I replaced the faulty switch 1 with new switch.
I connected all stacked cables between member 1 and other members of the stack.
Now If I turn on the new switch 1 with the same IOS as  other members of the stack I expect two thigs:
1 the new switch become  member 1 or member 5?
If it's visible as member 5 I can renumber it and I can reload only the new switch without affecting the stack right?
But if it's not joined to the stack I should reload all the stack then I expect  member 2 to become 1, member 3 to become member 2, member 4 to become member 3, the new member become 4?
If this happened it will be big trouble.
Because the 3750X switches are different, two copper switches and two SFP switches with different configuration and unique on the all members.
My goal is to replace the faulty member as soon as possible without any long interruptions and configuration mismatch.
Also how could I be sure that the new switch will not be the master after reload of the all stack?
Switch priority?
I identified this commands on the configuration:
switch 1 provision ws-c3750x-12s
switch 2 provision ws-c3750x-12s
switch 3 provision ws-c3750x-24
switch 4 provision ws-c3750x-24

I can set:
switch 4 priority 15 ( 15 is the high value and will keep switch 4 as master)
switch 3 priority 11
switch 2 priority 5
switch 1 priority1

The current state is:
#show switch
Switch/Stack Mac Address : f872.ea05.dd00
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
1 Member 0000.0000.0000 0 0 Provisioned
2 Member acf2.c5d5.3600 1 3 Ready
3 Member f872.ea4a.1380 1 3 Ready
*4 Master f872.ea05.dd00 1 3 Ready

During the incident when the member 1 failed, I turned off all members and firstly I started member 4 and after a 1 minute I started all other members.

[M02@rt37]

@tanner.zaitt,

Once the new switch is added and integrated into the stack, you can gradually increase its priority to allow it to become the new master. This way, you have more control over the master switch transition.

The new switch's priority should be set to a value lower than the current master's priority to prevent it from becoming the new master after a reload. The priority range is from 1 to 15, with 1 being the highest priority.

It should be better to these do theses changes during a maintenance window to minimize potential disruptions to your network.

[M02@rt37]

Perfect idea:

I can set:
switch 4 priority 15 ( 15 is the high value and will keep switch 4 as master)
switch 3 priority 11
switch 2 priority 5
switch 1 priority1

--Start Switch 4 first and then start the other members after a short delay.