vtp mode [mode]
Defines the operating state of the VLAN Trunking Protocol (VTP) on a switch. VTP automatically synchronizes the creation, renaming, and deletion of VLANs across an entire network, eliminating the need to manually configure VLANs on every single switch.
Quick Reference
Switch(config)#vtp mode serverSyntax & Modes
| Mode | Operational Behavior |
|---|---|
| server | The Default. You can create, modify, and delete VLANs. The switch broadcasts its VLAN database to the rest of the network and will update its own database if it receives an update with a higher revision number. |
| client | You cannot manually create, modify, or delete VLANs in the CLI. The switch strictly listens for VTP updates from servers and perfectly clones their database. |
| transparent | Modern Best Practice. The switch completely ignores VTP updates and maintains its own isolated, local VLAN database. However, it will pass VTP advertisements through its trunk ports to downstream switches. |
| off | Like transparent mode, but the switch entirely drops VTP frames instead of forwarding them. (Not available on all legacy IOS versions). |
CLI Deployment Scenarios
Scenario 1: Securing the Network (Disabling VTP)
Because of the severe risks of accidental VLAN wipes, most modern enterprise environments forbid VTP syncing. You configure the switch to ignore updates but still allow manual VLAN creation.
Scenario 2: Provisioning a New VTP Domain
If you are using VTP in a lab or legacy environment, switches will only sync if they share the exact same case-sensitive domain name and password.
CCNA Exam Gotchas
The VTP Revision Number Bomb
Every time you add or delete a VLAN, the VTP Configuration Revision Number increases by 1. Switches always trust the update with the highest number.
The Disaster: If you take an old lab switch (which has a revision number of 50 but no VLANs on it) and plug it into your production network (which has a revision number of 10 and 30 active VLANs), the production network will look at the higher number (50), assume the new switch is correct, and instantly delete all production VLANs to match the empty lab switch.
How to Safely Reset the Revision Number
Before connecting a used switch to a network, you must reset its revision number to 0. You can do this by either changing the VTP domain name to a bogus name and changing it back, or by temporarily changing the VTP mode to transparent and then back to server/client.