Reg : configuration revision number

Unanswered Question
Mar 27th, 2008

Hi Experts ,

Is there any commad to change the configuration revision number of Switch ?

If I want to change the coniguration revision number of switch what command I should use ?



I have this problem too.
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Jon Marshall Thu, 03/27/2008 - 01:07

Hi Satish

Do you mean the VTP configuration revision number ? If so there are 2 ways as far as i aware

1) Modify the vlan database on the VTP server, this will update the revision number and then all clients will update their number.

2) Change the VTP server to VTP transparent then back to VTP server again, this will reset the revision number to 0. Don't recommend doing this though as all the clients will then have a higher revision number and so they will ignore any VTP updates from VTP server switch.

Hope i've answered your question


smothuku Thu, 03/27/2008 - 01:55

Hi Jon ,

Thanks for the reply and info.

I read following from Cisco.

a VLAN database was introduced into Cisco IOS Software as a method to immediately save VTP updates for VTP clients and servers. In some versions of software, this VLAN database is in the form of a separate file in NVRAM, called the vlan.dat file. You can view VTP/VLAN information that is stored in the vlan.dat file for the VTP client or VTP server if you issue the show vtp status command.

VTP server/client mode switches do not save the entire VTP/VLAN configuration to the startup config file in the NVRAM when you issue the copy running-config startup-config command on these systems. It saves the configuration in the vlan.dat file. This does not apply to systems that run as VTP transparent. VTP transparent systems save the entire VTP/VLAN configuration to the startup config file in NVRAM when you issue the copy running-config startup-config command. For example, if you delete vlan.dat file after the configuration of the VTP in server or client mode and reload the switch, it resets the VTP configuration to default settings. However, if you configure VTP in transparent mode, delete the vlan.dat and reload the switch. This retains the VTP configuration.

You said that to cahnge the configuration revision number we need to modify the valn database.

Can you tell me the ways to modify the vlan database.

Is it possible to do changes to valn.dat file.



Jon Marshall Thu, 03/27/2008 - 02:42


You would modify the vlan database by

1) From enable mode type

switch# vlan database


And from there you can add, delete, modify vlan info if on VTP server.

Cisco are trying to move people away from this method.

2) From config mode on the switch

switch(config)# vlan


And from here you can add additional parameters.

This is recommended way to manipulate the vlan database now.

The above are IOS. On CatOS they are all "set vlan..." based commands.



smothuku Thu, 03/27/2008 - 03:27

Hi Jon ,

I've tried same on 3750G switch and noticed that whenever the switch is in server mode and addition or deletion of vlan is increasing the configuration revision by 1 which is accumulative.

In Clinet mode , we can't modify the vlan database.

What would be the max.value the configuration revision number can reach ?

How this value resets to zero once it reaches to max.



Jon Marshall Thu, 03/27/2008 - 03:45


The VTP configuration number is a 32bit unsigned integer so the maximum it can be is


I have no idea what happens when it wraps around as i have never experienced this.

Perhaps someone else knows the exact details ?


smothuku Thu, 03/27/2008 - 04:22

Hi Narayan ,

Valuable info..Thanks a lot.

Cheers :)


royalblues Thu, 03/27/2008 - 01:35

Yes it would..

Just a deviation from Jon's post, the client switches will not ignore the requests after it is changed back to server mode but rather update the server too with the revision number that is existing on their database.

They will be ignoring the request only when the domain names are different



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