Command
VTP Password
Use
This command secures VTP updates by setting a secure password.
Syntax
Switch(config)#vtp password <password>
Example

In the below example we will set a password of ‘cisco’ for the VTP domain.
SW1(config)#vtp password cisco |
SW2(config)#vtp password cisco |
Checking VTP status on both switches, we see that the MD5 digest matches. If it doesn’t, you’ll need to flap a few interfaces until VTP syncs up.
SW1(config)#do show vtp status |
SW2(config)#do show vtp status |