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Cisco 3750G Stack member switch drops port from spanning tree

cweindel
Level 4
Level 4

‎01-06-2011 09:49 AM - edited ‎03-06-2019 02:51 PM

Hello all,

I have two 3750G switch stacked using the stackwise cables.  On the member switch, when I change a switchport from VLAN 1 to any other VLAN, it drops the switch port from spanning tree and the light goes amber.  When I put it back to VLAN 1, it goes green.  VLAN 1 goes nowhere.  I'm running spanning tree mode MST.  This stack is trunked back to a 3750G core switch, just like all other stacks.  All other stacks communicate fine, and the configuration is consistant with the rest.  Why does the switchport "disappear"?

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10 Replies 10

Peter Paluch
Cisco Employee
Cisco Employee

‎01-06-2011 10:57 AM

Hello,

Does the other VLAN actually exist? Can you verify its existence in the show vlan brief output?

If the VLAN is successfully created, it would be interesting to see the MSTP configuration and running state. Can you please post the output of these commands?

  • show spanning-tree mst config
  • show spanning-tree

Thank you!

Best regards,

Peter

0 Helpful

cweindel
Level 4
Level 4
In response to Peter Paluch

‎01-06-2011 11:17 AM

thanks for your reply - i didn't check but the VLAN is there when I type "show vlan b" from the main prompt, but when I go to the member switch session (session 2) it is not!  Why are they not syncing up?

thanks for pointing me in a very solid direction!!

0 Helpful

Peter Paluch
Cisco Employee
Cisco Employee
In response to cweindel

‎01-06-2011 11:27 AM

Hello,

What do you exactly mean by "going to the member switch session"? A properly created 3750 stack behaves as a single switch and there are no sessions necessary to configure individual switches. Can you be more specific here?

Best regards,

Peter

0 Helpful

cweindel
Level 4
Level 4
In response to Peter Paluch

‎01-06-2011 11:35 AM

If you type "session 2" from a stack enable prompt, so can actually see what the member switch 2 is doing (in this case I only HAVE one member).  This is available as each switch in the stack runs its own spanning tree instance per VLAN, although the stack rings can never be blocked.  What I'm not sure of is if each switch has it's own VLAN database, or if it relies on the VLAN DB of the master (which is the way I understand it).  If that's the case, then that part doesn't matter on session 2.  But if it does, session 2 shows no VLANS, and it could be because I'm using VTP, and session 2 shows VTP mode as Server (when it should be client, with authentication).

0 Helpful

Peter Paluch
Cisco Employee
Cisco Employee
In response to cweindel

‎01-06-2011 11:53 AM

Hello,

Hmmm, the switch stack should behave as a single switch - share the same VLAN DB, the same VTP settings, ... Has the switch stack been created properly?

Best regards,

Peter

0 Helpful

cweindel
Level 4
Level 4
In response to Peter Paluch

‎01-06-2011 11:59 AM

As far as I know it has.  Does the interconnection of the stackwise cable matter?  At the moment there are connected like this:

MASTER    1 2

                    \  /

                     X

                    /  \

MEMBER    1   2

STACK1#sh sw stack-ring speed

Stack Ring Speed        : 32G
Stack Ring Configuration: Full
Stack Ring Protocol     : StackWise

STACK1#sh sw stack-p
  Switch #    Port 1       Port 2
  --------    ------       ------
    1           Ok           Ok
    2           Ok           Ok

0 Helpful

Peter Paluch
Cisco Employee
Cisco Employee
In response to cweindel

‎01-06-2011 12:33 PM

Hello,

The connection seems fine. Can you please also verify the show switch and show switch detail output?

Best regards,

Peter

0 Helpful

cweindel
Level 4
Level 4
In response to Peter Paluch

‎01-06-2011 12:30 PM

I just just checked another stack  - session 2 IS getting the VLAN info and the VTP info - unlike the problem stack.  The issue is, we've replaced that whole stack hardware - switches, cables, SFP modules - and it did the same thing!!  Confused, or the people who replaced the stack aren't being completely honest about it.

0 Helpful

Leo Laohoo
Hall of Fame
Hall of Fame
In response to cweindel

‎01-06-2011 01:01 PM 

On the member switch, when I change a switchport from VLAN 1 to any other VLAN, it drops the switch port from spanning tree and the light goes amber.
I agree with Peter.  On the stack master, can you enter the following commands:
1.  sh switch detail; and
2.  sh vlan brief

					
				
			
			
				
			
			
				
			
			
			
			
			
			
		

		
		
	

	
	


	
				
		
			
					
		
	
				
		
			
					
		
	
				
		
			
					
		
	
				
		
			
					
		
			
		
	
				
		
			
					
		
	
				
		
			
					
				
		
			
		
			
					
			
		
				
		
	
	


		

	

		

			

	
		
			
					

	
			

				
		
			
		
			
				

					
						
	
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I agree with Peter too.  Here's the output:
STACK1#sh sw detail
Switch/Stack Mac Address : e804.6245.3e00
                                           H/W   Current
Switch#  Role   Mac Address     Priority Version  State
----------------------------------------------------------
*1       Master e804.6245.3e00     2      0       Ready
 2       Member 0014.6a9f.1280     1      0       Ready
         Stack Port Status             Neighbors
Switch#  Port 1     Port 2           Port 1   Port 2
--------------------------------------------------------
  1        Ok         Ok                2        2
  2        Ok         Ok                1        1
STACK1#sh vlan brief
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Gi1/0/50, Gi1/0/51, Gi1/0/52
                                                Gi2/0/25, Gi2/0/26, Gi2/0/27
                                                Gi2/0/28
2    VSAT                             active
10   SWITCH_MGMT                      active
30   SERVER                           active    Gi1/0/13, Gi1/0/25, Gi1/0/26
                                                Gi1/0/27, Gi1/0/28, Gi1/0/29
                                                Gi1/0/30, Gi1/0/31, Gi1/0/32
                                                Gi1/0/33, Gi1/0/34, Gi1/0/35
                                                Gi1/0/36, Gi1/0/37, Gi1/0/38
                                                Gi1/0/39, Gi1/0/40, Gi1/0/41
                                                Gi1/0/42, Gi1/0/43, Gi1/0/44
                                                Gi2/0/3, Gi2/0/4, Gi2/0/5
                                                Gi2/0/6, Gi2/0/7, Gi2/0/8
                                                Gi2/0/9, Gi2/0/10, Gi2/0/11
                                                Gi2/0/12, Gi2/0/13, Gi2/0/14
                                                Gi2/0/15, Gi2/0/16, Gi2/0/17
                                                Gi2/0/18, Gi2/0/19, Gi2/0/20
                                                Gi2/0/21, Gi2/0/22, Gi2/0/23
                                                Gi2/0/24
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
110  FINANCE                          active
120  HR                               active    Gi2/0/1, Gi2/0/2
130  MARKETING                        active
140  SLOTS                            active    Gi1/0/1, Gi1/0/2, Gi1/0/3
                                                Gi1/0/4, Gi1/0/5, Gi1/0/6
                                                Gi1/0/7, Gi1/0/8
150  IT                               active
160  CAGE                             active    Gi1/0/9, Gi1/0/10, Gi1/0/11
                                                Gi1/0/12, Gi1/0/14, Gi1/0/15
                                                Gi1/0/16
170  FB                               active
180  MAINTFAC                         active
181  VALET                            active
190  SURV                             active    Gi1/0/17, Gi1/0/18, Gi1/0/19
                                                Gi1/0/20, Gi1/0/21, Gi1/0/22
                                                Gi1/0/23, Gi1/0/24
200  SEC                              active
210  CORP                             active
220  HOTEL                            active
1002 fddi-default                     act/unsup
1003 token-ring-default               act/unsup
1004 fddinet-default                  act/unsup
1005 trnet-default                    act/unsup
If your interested, here's the output from session 2, and it's inconsistant from other stacks:
STACK1-2#sh sw detail
Switch/Stack Mac Address : e804.6245.3e00
                                           H/W   Current
Switch#  Role   Mac Address     Priority Version  State
----------------------------------------------------------
 1       Master e804.6245.3e00     2      0       Ready
*2       Member 0014.6a9f.1280     1      0       Ready
         Stack Port Status             Neighbors
Switch#  Port 1     Port 2           Port 1   Port 2
--------------------------------------------------------
  2        Ok         Ok                1        1
STACK1-2#sh vlan b
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Gi1/0/45, Gi1/0/46, Gi1/0/47
                                                Gi1/0/48, Gi1/0/49, Gi1/0/50
                                                Gi1/0/51, Gi1/0/52, Gi2/0/25
                                                Gi2/0/26, Gi2/0/27, Gi2/0/28
1002 fddi-default                     act/unsup
1003 token-ring-default               act/unsup
1004 fddinet-default                  act/unsup
1005 trnet-default                    act/unsup
These should be identical.

					
				
			
			
				
			
			
				
			
			
			
			
			
			
		

		
		
	

	
	


	
				
		
			
					
		
	
				
		
			
					
		
	
				
		
			
					
		
	
				
		
			
					
		
			
		
	
				
		
			
					
		
	
				
		
			
					
				
		
			
		
			
					
			
		
				
		
	
	


		

	

		

			

	
		
			
					

	
			

				
		
			
		
			
				

					
						
	
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