Behavior when changing VTP transparent to VTP client

Unanswered Question
May 15th, 2012
User Badges:

In the following scenario, how will the 2950/2960/2960S series behave:


- VTP server/domain configured on a 6509

- A access switch (2960) currently configured in transparent mode with all VLAN it requires


Will the switch drop any traffick if we change it from transparent to client mode if the VTP server has the exact same vlans defined as the access switch had when it was in transparent mode?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
cammaher Mon, 04/01/2013 - 20:29
User Badges:

Hi,

Have you got an answer to your question as I have exactly the same issue at the moment.


Thanks,

Cam

Rolf Fischer Mon, 04/01/2013 - 22:46
User Badges:
  • Blue, 1500 points or more

Hi,


when you change the VTP mode from transparent to client, the switch will initially set it's configuration revision to 0 and keep the VLAN-information until it receives better information (configuration revision > 0). If there are no differences to the local VLAN-config, there won't be any outage.

I've done this serveral times; the only problem I ever had was related to VTP pruning. So I'd recommend to disable pruning (if enabled) until you're ready with your changes and all the switches in the domain have the same VTP information. Then you can safly re-enable it.


Hope that helps

Rolf

InayathUlla Sharieff Mon, 04/01/2013 - 23:38
User Badges:
  • Cisco Employee,

Hi,

Let me try to explain you:



1- VTP Transparent.



What ever vlans are been configured under the VTP transparent mode will only be available to view when the switch is in the transparent mode. ( You dont see the ocnfiguration revision number increasing when you go on adding the vlan under the transparent mode.) Hence when you change the mode from transparent mode to client mode all the vlans which were configured under the transparent mode will be wiped out hence when it recieves the vtp packet from the server it gets it vlans updated as the revision number would be greater than 0.



Eg:



Currently switch in transparant mode;



Switch#sh vtp st

VTP Version                     : 2

Configuration Revision          : 0 <<<<<<<<<<<, Config revision doesnt get increased when we add any vlans.

Maximum VLANs supported locally : 255

Number of existing VLANs        : 11

VTP Operating Mode              : Transparent

VTP Domain Name                 : cisco



Switch#show vlan  ( 7 vlans are been configured)





VLAN Name                             Status    Ports

---- -------------------------------- --------- -------------------------------

1    default                          active  

10   VLAN0010                         active   

20   VLAN0020                         active   

30   VLAN0030                         active   

40   VLAN0040                         active   

50   VLAN0050                         active   

60   VLAN0060                         active   



2- Now I will change the transparent to client:



Switch(config)#vtp mode client

Setting device to VTP CLIENT mode.



sh vtp st

VTP Version                     : 2

Configuration Revision          : 2  <<< Config revision has been changed.

Maximum VLANs supported locally : 255

Number of existing VLANs        : 7<<<<<<<<<<<<<<<< This are the vlans which were pulled from the other switch which is the server.

VTP Operating Mode              : Client

VTP Domain Name                 : cisco




Switch#sh vlan



VLAN Name                             Status    Ports

---- -------------------------------- --------- -------------------------------

1    default                          active   

10   VLAN0010                         active   

20   VLAN0020                         active 



You dont see other vlans which you had configured under the transparent mode. But what ever vlans are available/configured on server will be pushed to the client and gets updated. In my case I only have 2 vlans configured on the server hence those are been updated under client.


HTH

Regards

Inayath

*Plz rate if this info is helpfull.

Neeraj Arora Tue, 04/02/2013 - 05:02
User Badges:
  • Silver, 250 points or more

Although as per me, answer to your query has been already provided with good amount of details (and yes VTP-pruning does cause problems if enabled unneccessarily), still I would like to chip in by saying that:

Changing the VTP mode from Transparent to Client, assuming that VTP domain name & password is correct/matching with the VTP server AND the vlans in both the switches are same, then traffic will not be dropped except for a seconds delay (or even less) taken by VTP convergance

cammaher Tue, 04/02/2013 - 15:16
User Badges:

Thanks very much for the answers everyone.

My other question regarding this is what would happen in the following scenario.


Switch 1 is configured for VTP Transparent mode and has VLAN 20 configured. A number of the intergfaces are placed in VLAN 20.


On Switch 2 which is a VTP Server, there is also a VLAN 20 configured.


(I understand that the two VLAN 20's are in different VTP domains, so are in effect, totally difference, separate VLAN's).


Now, if  I change Switch 1 to be in VTP Client mode and part of the same VTP domain as Switch 2, I understand that the VLAN 20 on Switch 1 is removed and replaced with VLAN 20 from Switch 2 (VTP Server).


What happens to all of the interfaces on Switch 1 that are in VLAN 20. Do they remain in VLAN 20 and now participate in the Switch 2 (VTP Server) VLAN 20, or do they automatically go back to VLAN 1. Do they go into err-disable mode or something similar?


Thanks again for all your help.

paul driver Tue, 04/02/2013 - 16:13
User Badges:
  • Green, 3000 points or more

Hello,

When changing the vtp mode of a switch from transparent to client the the revision number will go from a zero value to that of the vtp server revision number.


Now:
1)  if your vtp server has vlans that your now vtp client doesn't have then the now vtp client switch will be updated with these additional vlans.


2)  if your vtp client switch has vlans that your vtp server doesn't have then these vlans will be deleted from the vtp client switch becasue the vtp server will overwrite the client switch database..


All interfaces will remain as they were unless the vlans they resided in are deleted due to the above changes


res

Paul





Please don't forget to rate any posts that have been helpful.


Thanks.

cammaher Tue, 04/02/2013 - 16:16
User Badges:

Thanks Paul.


When you say "All interfaces will remain as they were unless some vlans are deleted due to the above changes", exactly what will happen to the interface configuration and state if a local VLAN is deleted due to the change.

paul driver Tue, 04/02/2013 - 16:19
User Badges:
  • Green, 3000 points or more

Hello

They will stop communicating  untill that vlan is recreated on the client switch or on the vtp server switch


conf t

vlan xx

exit


res

Paul



Please don't forget to rate any posts that have been helpful.


Thanks.

InayathUlla Sharieff Tue, 04/02/2013 - 17:37
User Badges:
  • Cisco Employee,

HI Cam,

As suggested when you move from Transparent mode to any mode all the existing vlans will be deleted hence you will be on no vlans configuration on the switch. When it gets pulled by or updated by server assuming that you have correct VTP domain name,password and the trunk between the switches are fine then the switch gets updated with all the vlan information from the server. If in case the vlan which was configured on Transparent and not on server then you need to add that/those vlans on the server mode else the users who were configured with the vlans on the transparent will not work as expected.


hope this clarifies your doubt.


HTH

Regards

Inayath

Please don't forget to rate any posts that have been helpful.

Actions

This Discussion

Related Content