How to delete vlan?

I'm doing ccna NetAcademy labs on VLAN. Three switches are connected to each other. I created a bunch of vlans on the switches. After I'm done with the lab, I delete vlan.dat and startup.config and reload the three switches for my next lab. But to my surprises, the Vlans from last lab stayed on the switches.

I guess it's because all three routers are connected to each other. When I delete vlan.dat and reload one switch, it grabs vlan info from its neighbor before I had a chance to reload its neighbor. Is that the case? If so, do I have to disconnect the cables to prevent this from happening?

After that if I created a new vlan on one of the switches, the other two switches would have that vlan too, even without any IP set up on them. What protocol does it use to make this happen?

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Comments

d6bmg

Check whether the VTP is turned on or not.

pamccabe

A good rule of thumb, in a production environment anyway, is to configure the switch before you place it in production. That being said, in your situation, you could configure it to be transparent and then reload the switch. When it comes back up, it will still be in transparent mode. At least that is how it always worked in Packet Tracer when I messed around with it. In transparent mode, the vlan database won't be updated, but it will forward vtp frames. Hope that helps.

RouteMyPacket

What is the VTP mode?

Do a "sh vtp status", if it's a client you can't manipulate the VLANs there. Must be on the "server"

Transparent mode?

conf t
no vlan 10
exit
no vlan 20
exit
no vlan 30

sh flash (see the vlan.dat there?)
delete flash:vlan.dat

confirm deletion

Something like that.

leonlimsg

This is caused by VLAN Trunking Protocol(VTP).

It is used to pass VLAN information(add, delete, rename etc) between switches if the swtiches are in the same VTP domain.

There are three types of VTP modes:

- server mode
- client mode
- transparent mode

Please google to find out what each mode can perform.

Lastly, a client with a higher revision number can overwrite the settings in the server. So before you connect a switch to a network, do ensure the revision number is not higher than the switch in server mode.

pamccabe

It's good to change the mode from transparent, back to client. Going from transparent to another mode will reset the revision number. Also, VTP is a layer 2 protocol. It uses a layer 2 multicast to send out updates. That is why it works without an IP setup on them.

Danielh22185

RouteMyPacket wrote: »

What is the VTP mode?

Do a "sh vtp status", if it's a client you can't manipulate the VLANs there. Must be on the "server"

Transparent mode?

conf t
no vlan 10
exit
no vlan 20
exit
no vlan 30

sh flash (see the vlan.dat there?)
delete flash:vlan.dat

confirm deletion

Something like that.

^^This should take care of it.