Is VTP enabled by default on a Cisco IOS 15.x switch?

[David Anderson]

My instructor led course (Chris Bryant) advises it is not on by default in his videos, but I understand that these are older videos so I occasionally have to research updated information.

I see my 3750v2 switches running 15.x IOS running VTP v1 after doing a write erase / delete flash:vlan.dat / reload on all my switches, and I'm wondering if that is correct.

I researched and I found something about the switch runs VTP in a non-management domain until it is contacted and updates or something, but I'd like to know - Does VTP run by default on a Cisco 15.0 switch? Are my switches running v1 an IOS image bug?

Any input appreciated, thanks!

[Leo Laohoo]

Not enabled if VTP Domain and VTP password is not set.

[David Anderson]

Would that be the case, even if I type "sh status" after wiping a switch / vlan.dat, and when it comes up I immediately do "sh vtp status" and it shows Version 1 is running.

Is there not a definitive Yes or No to that without condition, everything I read is a grey area on this, like its sitting in some dormant state turned on but not actively working until it receives an update or like said is configured with a domain name / password.

Is there no flat Yes or No answer to if its enabled on a switch out of the box, like how CDP is enabled?

[BradEast1]

The actual protocol (VTP) will be on by default but is not doing anything until you configure a domain name and password.

[Mark Malone]

Hi

we dont use vtp it can be dangerous if not implemented correctly the whole revision number issues of wiping switches , if your going to use it i would only use vtp3 or turn it off with vtp transparent

vtp v1 is on by default on all switches but in the Null domain only , without domain set as Leo said it wont send any messages to other switches , v1 and v2 you can turn it off with transparent , i think from when i tested v3 there is an actual command to turn it off too in that version only

[Julio E. Moisa]

Hi

By default all the switches are configured with VTP Server mode and it includes all default parameters, like NULL domain.

A best practice is suggested configure the switches in transparent mode before to install them on your network infrastructure to avoid any problem. 

On the new switch models you will find the following modes:

client Set the device to client mode.
off Set the device to off mode.
server Set the device to server mode.
transparent Set the device to transparent mode.

If you don't want to take any risk with VTP, you can set up one of the following modes on your switch: transparent or off, the last one will disable it. 

Hope it is useful

:-)

[David Anderson]

Stars all around for building up a full response to my questions, thanks for your input, I appreciate it!

[Predrag Jovic]

Actually, as soon as VTP domain name is configured VTP will start function (it is on - default vtp mode is server).

VTP messages will be sent as soon as trunk is established and domain name configured.

Password must match, empty password is "good enough", password does not need to be configured.

It is easy establish above by using debuging

debug sw-vlan vtp packets

debug sw-vlan vtp events

debug sw-vlan vtp xmit