How can VTP help me?
In other words, the job of VTP is to distribute VLAN configuration information between all the switches.
How does it work?
The job of VTP is best explained from the perspective of the VTP server. All switches, by default, are VTP servers. The VTP server is where you would create, remove, or modify VLANs.
This VTP server sends an advertisement, across the domain, every 5 minutes or whenever a change is made in the VLAN database. That advertisement contains all the different VLAN names, VLAN numbers, what switches have ports in what VLANs, and a revision number. Whenever a switch receives an update with a larger revision number than the last one it applied, it applies that revision.
Keep in mind that VTP is a Cisco proprietary protocol. So, to use VTP between your switches, you must have all Cisco switches.
- Server – the default where all VLAN adds, changes, and removals are allowed
- Client – where no changes can be made, only new revisions can be received from the VTP server switches.
- Transparent – where local VLAN information can be changed but that information is not sent out to other switches. Transparent switches also do not apply VTP advertisements from other switches but they do forward those advertisements on.
What about pruning?
Pruning saves LAN bandwidth because broadcasts don’t have to be sent to switches that don’t need them.
How do you configure VTP?
- VTP domain – the name of the VTP domain. All switches communicating with VTP in the same domain, must have the same VTP domain name.
- VTP mode – either server, client, or transparent
- VTP password – a password to control who can and cannot receive VTP information
- VTP pruning – VTP pruning is either turned on or off
To see what is going on with VTP, you can use show vtp status, like this: