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Incorrect LED light outputs on 3750 stack

We have 3 x c3750g switches cabled together in a stack. They each have the same software versions, and no errors are shown on the CLI (show switch detail command shows all OK, with 1 master switch and two member switches).

The problem is that the physical LED output on each switch is showing random LEDs lit - even though the stack is working OK. Two of the three switches have the master LEDs showing green. Could this be a problem with the stacking cables or the physical stack ports on the rear of the units? Could this be a problem with the motherboards?

Any help would be much appreciated..


How have you cabled your switches?!

This link gives you a good idea of how to cable, even knowing that the stack is working... well, it's always a worth try to use the standart:

Also... have you set the priority on the switches, or they have elected as master automatically?!

When you issue a show switch command, you can check which switch is the master, and if you want to set the priority manually (I do recommend you to do so), just use the command:

switch priority 15

for the second switch set priority 14, and the third priority 13. It works just fine with this... If you want to renumber any switch (like it's 1/0/1 and you want it to be 2/0/1 for example) just use the command:

switch renumber


switch 1 renumber 2

That is also a good idea to do so you don't have like the third switch with ports 2/0/0, 2/0/1, 2/0/2 and so on...

Let me know if that helped!


Caue Wailemann


Hi Caue,

Thanks for your reply.

I used the Cisco standard cabling model (and tried every other combination possible!)

Switch numbering is:

switch 1 priority 15

switch 2 priority 1

switch 3 priority 1

I'll try your combination (15,14,13)later today when I go back to the office..

I tried to build the original stack with three switches to start with - is this recommended?

Thanks again - I'll let you know how this goes..



yeah... 3 switches, 4, 5... I just finished the installation of a stack with 7 3750 switches and it worked just fine...

What do I usually do... I just power-up each switch individually without the stack and them I assign to it the priority and the switch number, like for the first switch:

switch 1 priority 15

switch 1 renumber 1

for the second:

switch 1 priority 14

switch 1 renumber 2

and I do that for every single switch, always decreasing the priority until the end. Just after that, I power off my switches and cable the stack. I power the first switch, wait 5sec, power the second, more 5sec, power the third, and so on.

It works each and every time without any headaches... Off course, this is only possible in a new installation, or in a network where you can get some downtime, but is a worth try.

Let me know if things are working for you or not!


Caue Wailemann

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