Stacking Problem, Both switches act as master

Unanswered Question
Jul 8th, 2007
User Badges:


I have two cisco 3750 switches that i want to stack. All four switches have same model and same ios. Physical connectivity and general configuration like (switch ID, priority etc) are fine.When i powered on a switch with higher priority to become master and after 20 sec power on second switch, both switches become master after completion of booting process. While booting process , i get the messages below:

00:01:28: %STACKMGR-4-SWITCH_ADDED: Switch 7 has been ADDED to the stack

00:01:29: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down

00:01:31: %SPANTREE-5-EXTENDED_SYSID: Extended SysId enabled for type vlan

00:01:33: %SYS-5-CONFIG_I: Configured from memory by console

00:01:33: %STACKMGR-5-SWITCH_READY: Switch 7 is READY

00:01:33: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 7 has changed to state DOWN

00:01:33: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 7 has changed to state DOWN

00:01:33: %STACKMGR-5-MASTER_READY: Master Switch 7 is READY

Switches Specifications:

Model: WS-C3750G-24TS-E

IOS: c3750-ipservicesk9-mz.122-25.SEE3.bin

Stacking Cable: Standard Cisco Cable

Waiting for your positive response.



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Amit Singh Sun, 07/08/2007 - 21:08
User Badges:
  • Cisco Employee,


Trusting that Switch ID and priorities have been configured and working correctly, Please ensure that the stackwise cables are connected securely. Which ports are you plugging them into on each switch? Here is a url that discusses some possibilities for installation:

Check if all the switch stackports are active and working. Try swapping the stack cable between different switches and see if the same problem follow the cable on another switch.


-amit singh

rameezsardar Sun, 07/08/2007 - 21:43
User Badges:

Dear Amit,

I am sure that stack cables are connected correctly in cross way means stack port 1 of first switch is connected to stack port 2 of the other and also i have changed cables but problem still there. Tell me one thing is there any specific configuration related to vlans, vtp domain, stp etc. for stacking?

Stacking Ports are working fine. When i issue command show switch stack-port, it shows both port with down state and #show switch command shows both switches are masters.

Waiting and Regards


Amit Singh Sun, 07/08/2007 - 22:17
User Badges:
  • Cisco Employee,


As such there is not speacial config for VTP/STP for stacking. How many switches you have in totallity.You said you have 2 switches to stack and all 4 switches are working fine?

Please paste the output of " show platform stack-manager all ".

-amit singh

rameezsardar Sun, 07/08/2007 - 23:14
User Badges:

Dear Amit,

Thanks for responding. Actually i have four switches but want to stack just two. Sorry for that mistake. Output of command "show platform stack-manager all" u can find in attachment because of character limitation i cann't past it.

Thanks and Waiting

Amit Singh Sun, 07/08/2007 - 23:54
User Badges:
  • Cisco Employee,


The output shos to me that both the switches are unable to exchange the stack information with each other and have independently become the master. The stack ports are showing down/down which shows that these switches are not exchanging the stack information.The ports should be ok/ok for proper stack functionality.

There coule be many reasons for this :

1. Faulty stack cable: As you have already tried swapping the cable, Please make sure that a proper working cable was used for the same.

2. Faulty stackports : To diagnose this, Please try using some other switch instead of switch7 and see if you observe the same behaviour. Try using all the different switches to diagnose this problem.

3. IOS Bug: I will try to findout a possible IOS bug for the same and update you on the same. I have come across a bug where adding a 6th switch to a running stack of 5 switches shows the same symptoms but I am not sure if we can relate that to the problem that we have.

Please try diagnosing the Steps 1 & 2 and let me find out a bug for this:

-amit singh

rameezsardar Mon, 07/09/2007 - 21:23
User Badges:


I have verified Step 1 & 2 and both are OK. As i told you that i have 4 switches and 4 stack cables, i have tried all possible combination and still unable to stack two or more switches. Can it be a possibility that ios having bug?

Should i try any other ios?



Amit Singh Tue, 07/10/2007 - 02:57
User Badges:
  • Cisco Employee,

Yeah, We can try uploading the new IOS on the switch. Lets try that out and see if that works for us. Please keep me posted on the same once the upgrade is done.


-amit singh

glen.grant Tue, 07/10/2007 - 06:36
User Badges:
  • Purple, 4500 points or more

Set the priority on the switch you want as stackmaster to 15 and the other switch to 14 before starting . Power up up the master for a couple minutes then power the 2nd switch .

rameezsardar Tue, 07/10/2007 - 07:27
User Badges:


I have done this priority sequence but failed. Even I upgraded ios from "c3750-ipservicesk9-mz.122-25.SEE3.bin" to new ios "c3750-advipservicesk9-mz.122-37.SE.bin" but problem is still there. One thing is important that number of new messages are appearing that you can find in attachment.

Some Important messages, i am pasting below

SM: Detected stack cables at PORT1 PORT2

Waiting for Stack Master Election...

SM: Waiting for other switches in stack to boot...


POST: PortASIC CAM Subsystem Tests : Begin

POST: PortASIC CAM Subsystem Tests : End, Status Passed

POST: PortASIC Port Loopback Tests : Begin

POST: PortASIC Port Loopback Tests : End, Status Passed

Election Complete

Switch 3 booting as Master

Waiting for Port download...Complete

00:01:26: %STACKMGR-4-SWITCH_ADDED: Switch 3 has been ADDED to the stack

00:01:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down

00:01:29: %SPANTREE-5-EXTENDED_SYSID: Extended SysId enabled for type vlan

00:01:31: %SYS-5-CONFIG_I: Configured from memory by console

00:01:31: %STACKMGR-5-SWITCH_READY: Switch 3 is READY

00:01:31: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 3 has changed to state DOWN

00:01:31: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state DOWN

00:01:31: %STACKMGR-5-MASTER_READY: Master Switch 3 is READY

Now What you say?

Thanks and Regards


rameezsardar Wed, 07/11/2007 - 00:32
User Badges:


Ok tell me onething, how can i remove the existing stacking configuration like switch number,priority etc and bring back to default like a brand new router?

Tell me one thing more, where switches save its stacking information (of course not in startup)?

Waiting for response again.......




This Discussion