Trunk between a 3750 stack and a 3550

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Jul 12th, 2010
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I am sure sombody else has encountered this before:

I have stack of 5 x 3750 switches configured with several VLANs, no issues. (VTP is set to Server on this stack)

I also have an older 3550 which has a trunk interface conneciting to the 3750 stack. (VTP is set to Client on this switch)

When I add a new VLAN on the 3750 stack, I don't see this update propagate to the 3750. No VLAN pruning going on. Here is the config. (Note that the VLAN in question is VLAN 888, no showing in the VTP Client (3550). Infact there are several VLANs not showing on the Client.

On 3750 stack (VTP SERVER):

Sh int trunk:

Port                Vlans allowed and active in management domain
Gi1/0/49            1,10,20,30,40,50,60,66,70,80,88,90,100,105,110,200,300,400,600,800-801,888,900

On 3550 (VTP CLIENT):
Sh int trunk:

Port      Vlans allowed and active in management domain
Gi0/1     1,10,20,30,40,50,60,70,80,100,105,200,400,600,800-801

Am I supposed to manually add vlans to the trunk on a VTP Client? sine the Server is already allowing the VLAN on the trunk interface, I assume the manual add should be in the client trunk interface (?) Can somone provide the command line configuration? Most importantly mI need to avoid any outages. Will the change create an outage?


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Jon Marshall Mon, 07/12/2010 - 10:43
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Can you post

1) "sh vlan brief" from the stack and the 3550

2) sh run from the 3750 and the 3550


KavehSheikh_2 Mon, 07/12/2010 - 14:32
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For some reason I cannot log on to COO anymore. I just reset my pass. I will upload the configs as soon as I reset my pass, but it seems problematic (?)

KavehSheikh_2 Mon, 07/12/2010 - 14:36
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Ok thanks Jon. The information you requested in attached.

Note the trunk in question is on port Gi0/1 on the Access switch and on 1/0/49 port on the core switch.

Also the VLAn 888 showing on the ACCESS switch was manually created in the troubleshooting process, but ot really doesnt worlk. As you will see, some of the VLANs are are not being 'learened' by the the client.


Jayakrishna Mada Mon, 07/12/2010 - 14:41
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Can you also post show vtp status from both switches.



KavehSheikh_2 Mon, 07/12/2010 - 14:50
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Here you go below (Note: I am aware of VTP version mismatch, and the Access switch does generate a log every now and then about this, but based on my understanding this is not the root cause. I read earlier today that a VTP version mismatch should not impact the trunk in this way - The specific log is: " Jul 12 16:44:47.775: %SW_VLAN-4-VTP_USER_NOTIFICATION: VTP protocol user notification: Version 1 device detected on Gi0/1 after grace period has ended"). Thanks


VTP Version : running VTP1 (VTP2 capable)

Configuration Revision : 18

Maximum VLANs supported locally : 1005

Number of existing VLANs : 27

VTP Operating Mode : Server

VTP Domain Name : COMPVTP

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0xAD 0x63 0x93 0x06 0x83 0x4F 0x68 0x5E

Configuration last modified by at 6-15-10 12:26:33

Local updater ID is xx.xx.xx.xx on interface Vl10 (lowest numbered VLAN interface found)


VTP Version : 2

Configuration Revision : 28

Maximum VLANs supported locally : 1005

Number of existing VLANs : 20

VTP Operating Mode : Client

VTP Domain Name : COMPVTP

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0xB8 0xF2 0x10 0x49 0xE0 0xB2 0x95 0xBA

Configuration last modified by xx.xx.xx.xx at 11-7-07 22:12:08


Jayakrishna Mada Mon, 07/12/2010 - 17:11
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I have seen this with the version mismatch, so you might want to change the version and check.

Second thing that I notice is Config-rev number on client is  28 while the server is 18 so any updates . Since version 1 is not comaptible with version 2 client is not overwriting is the database on the serve,r if they were both running ver 2  it would have overwritten the database on server.


KavehSheikh_2 Tue, 07/13/2010 - 05:49
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Thanks. Does changing VTP version create a down time? If yes, I assume there would be less impact if I change the VTP version on the Access switch from v2 to V1. I appreciate your help.




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dichatte Mon, 07/12/2010 - 18:41
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Also would like to mention that is the if the vlans on the client were added there from before,it was added to the Server through trunk.

Also check if there is VTP password set or not, which may be restricting the client from getting update.

NoChanceIV Tue, 07/13/2010 - 14:22
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Be very careful with this. Remember, the higher Revision writes to the lower Revision, even if the higher Revision is in Client mode. If the Access switch had been working correctly, you could have messed up the VTP domain on the VTP Server switch.

If I was you, I would change the Access switch VTP to transparent before making any additional VTP changes. Once you've done that, the Revision number will reset to 0. Then fix the Version mismatch and check the VTP password. After that, then change the VTP back to Client. If all goes well, it should pull the VLAN's from the VTP Server.

Good Luck.



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