How to remove VTP domain

Unanswered Question
Sep 8th, 2009

Hi, Someone might ask the same question before but I can't find it.

I just want to clear/remove the VTP domain from my switches(2900/3550/4948), but can't succeed.

Can anyone advise what the command to acheive it? TIA!

I have this problem too.
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Lucien Avramov Tue, 09/08/2009 - 13:51

You can not remove the domain from the configuration, you can change it on will.

If you want to remove it, the way I know to get it back blank is a write erase on the switch.

David Lin Tue, 09/08/2009 - 13:54

Thanks! Lucien.

Althrough this is not a good news for me, but really appreciate your swift reply.

Edison Ortiz Tue, 09/08/2009 - 13:55

the way I know to get it back blank is a write erase on the switch.

That won't do it unless you are running VTP transparent - which is no VTP after all.

The VTP information is stored in vlan.dat which is not part of the running config.

__

Edison.

Lucien Avramov Tue, 09/08/2009 - 14:02

A write erase does remove the vtp information.

Try it in the lab.

Also when you are in server mode, you can still have no config for the domain name if you did not have any and you were in transparent mode before:

NMS-CAT6K-B(config)#vtp mode server

Setting device to VTP Server mode for VLANS.

NMS-CAT6K-B(config)#exit

NMS-CAT6K-B#show vtp sta

VTP Version : 3 (capable)

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 11

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

Edison Ortiz Tue, 09/08/2009 - 14:19

A write erase does remove the vtp information.

Rack1SW4#sh vlan

VLAN Name Status Ports

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

1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16

Fa0/17, Fa0/18, Fa0/19, Fa0/20

Fa0/21, Fa0/22, Fa0/23, Fa0/24

Gi0/1, Gi0/2

10 VLAN0010 active

100 VLAN0100 active

Rack1SW4#sh vtp status

VTP Version : running VTP1 (VTP2 capable)

Configuration Revision : 3

Maximum VLANs supported locally : 1005

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x58 0x85 0x1C 0x56 0x04 0xE8 0x79 0x5F

Configuration last modified by 0.0.0.0 at 3-15-93 12:00:30

Local updater ID is 0.0.0.0 (no valid interface found)

Rack1SW4#

Rack1SW4#wr er

Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]

[OK]

Erase of nvram: complete

Rack1SW4#

*Mar 9 09:07:22.614: %SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram

Rack1SW4#

Rack1SW4#reload

System configuration has been modified. Save? [yes/no]: n

Proceed with reload? [confirm]

*Mar 9 09:07:43.370: %SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload command.

--- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [yes/no]: n

Would you like to terminate autoinstall? [yes]: y

Press RETURN to get started!

Switch>en

Switch#sh vtp status

VTP Version : running VTP1 (VTP2 capable)

Configuration Revision : 3

Maximum VLANs supported locally : 1005

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x58 0x85 0x1C 0x56 0x04 0xE8 0x79 0x5F

Configuration last modified by 0.0.0.0 at 3-15-93 12:00:30

Local updater ID is 0.0.0.0 (no valid interface found)

Switch#sh vlan

VLAN Name Status Ports

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

1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16

Fa0/17, Fa0/18, Fa0/19, Fa0/20

Fa0/21, Fa0/22, Fa0/23, Fa0/24

Gi0/1, Gi0/2

10 VLAN0010 active

100 VLAN0100 active

This switch is standalone, but let me verify there is no trunk from another switch

Switch#sh int trunk

Switch#

Also when you are in server mode, you can still have no config for the domain name if you did not have any and you were in transparent mode before:

Don't quite follow but if you mean - you can have a null domain name, yes - that's the default but no VTP updates and newly created Vlans will be advertised until there is a VTP domain name in the switched network.

__

Edison.

Edison Ortiz Tue, 09/08/2009 - 14:26

Can you write erase in your switch and see the Vlan information disappear?

So, we need to update this document based on your findings..

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml

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.

__

Edison.

Lucien Avramov Tue, 09/08/2009 - 14:27

I'll check and respond back here.

Thanks

Edison Ortiz Tue, 09/08/2009 - 13:51

You can't clear the VTP domain once entered without erasing the vlan.dat from the switches.

You can change the VTP domain to another name.

What exactly is your goal? Start with a new VTP domain and Vlans - factory default?

__

Edison.

David Lin Wed, 09/09/2009 - 17:58

Thank you all. I was in the datacenter and just saw these replies now.

Actually the VTP is running properly on my prodution network. We recently got a ethernet cross connection for two sites in a buliding. But there is 3rd party switch which is controled by buliding in this link. I can't set up the dot1q VLAN trunk between our 2 Cisco switches in each site over this link.

I suspected this is VTP domian issue which is blocked by 3rd party switch. That's why I was trying to remove VTP domain name. But I just realized this may not be possible unless the buliding switches setup the VLAN trunk with my Cisco switch(if my understanding is correct, but this is another queston though).

I understand the VTP domain name will be removed by deleting vlan.dat,but it also removes my VLAN setting that is not allowed do on prodution network (Don't know why IOS works like this way).

Edison Ortiz Wed, 09/09/2009 - 19:58

If the 3rd party switch is between the 2 Cisco switches, you won't be able to pass the Vlan information unless the 3rd party participates in your switch domain.

In order to send Vlan information you need to have a VTP domain name, it can't be null so asking to remove the name so updates can be sent via the 3rd party switch is pretty much a lost cause.

You can work around this dilemma by setting a L2TPv3 connection between 2 Cisco routers. The Cisco routers will provide a L2 Tunnel for your 2 Cisco switches and bypass the 3rd party switch.

__

Edison.

MUHAMMAD SHAHEEN Thu, 09/10/2009 - 02:22

Hi,

to change the vtp domain name back to default, you just need to change delete vlan.dat from the flash without deleting the configuration.

The configuration will be preserved and vtp will go back to factory default with no domain.

I did it a while back more than 1 year ago!!! not recently unless the new IOS releases do not allow this.

Hope This Helps....

Shaheen

iyde Sun, 09/13/2009 - 05:09

Edison,

What about "switchport nonegotiate" and "switchport mode trunk" on the trunks going to the third-party switch in order to make the trunk come up? Of course we then have to make sure that the third-party switch have the right VLANs configured and allowed on the trunk port towards the two Cisco switches, but isn't it what it takes to make the schenario work?

Edit: The two areas will then be in different VTP domains, but I assume this will be no big deal?

In regard to setting VTP to default: I remember something about that the default domain is 'null' and the default mode is Server. But if the switch then _receives_ a VTP update, it will assign itself the domain name from this update and subsequently inherit the VLAN database from the neighbor switch (or the current VTP server).

Comments to that?

HTH

Edison Ortiz Sun, 09/13/2009 - 06:17

The issue is not the trunk. The issue is the 3rd party switch additional configuration (i.e: creating Vlans) to forward the required Vlans as a transit L2 device. The trunk will come up even without the 'switchport nonegotiate' but the tagging information will be dropped on the next hop, the 3rd party switch.

802.1q header information will be preserved from switch to switch as long as the required Vlans are created on each switch. VTP just eases the process and maintains an uniform database.

You are correct on the process on the domain name assignment when a VTP update is received.

HTH,

__

Edison.

MUHAMMAD SHAHEEN Sun, 09/13/2009 - 09:14

Ingolf,

Yes, the default domain name is null and mode is server.

To avoid this situation of inheriting VLAN database from a neibor switch, one should set the domain name and/or at least configure a ntp password and/or simply change the mode to transparent before inserting this switch in production.

Hope This Helps....

Shaheen

YANGCCIE4 Sat, 09/19/2009 - 09:05

Try this step in your lab first,

1, change the vtp domain into transparent mode, copy the configuration into notepad,

2, delete the vlan.dat file and config.text, and write erase the system configure,

3, reload the device, copy the configuration back to your system, and don't forget change the vtp mode back to the original mode.

4, configure other vtp parameters except the vtp domain.

hope it help

Yang

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