VTP

VTP(VLAN trunking protocol)

Used to dynamically add, remove and update VLANs(2-1000) Not really used much anymore. Its a Cisco proprietary protocol. I had a jr engineer that I worked with that was pretty close to implementing VTP at one time. I guess if his configs were valid we should have let him go through with it.


One other thing to add, is that this is not a trunking protocol such as ISL or 802.1Q. What we are doing with VTP is creating vlan's in once place and letting them replicate to other devices.


So now onto VTP

VTP packets are sent in the frames of ISL, and 802.1Q message, and it contains the following information.

- VTP version 1,2 or 3
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VTP Join Message

Management Domain Length
Management Domain Name

VTP also has a configuration revision number which let shows the which revision
VTP is currently on, this is important as we will soon discover. When a switch receives a revision that is higher than its own it will act on it.





3 modes
-Server
-Client
-Default


Server
The default mode. This is the one that can change VLANS, Sends and receives VTP updates.(2-1000) are configurable

Client
Takes orders from the server.
Sends and receive updates

Transparent(recommended mode)
Can change Vlan info
Just passes through Vlan configs to other switches
Does not act on VLAN advertisements
always at revision 0
The switches need to be in transparent mode to configure extended Vlans (1006-4096)


Authentication
Domain names and passwords can be setup to allow for protection throughout your network. Make sure you have a separate name for Lab and Production switches, as this will cause some pain later on.


VTP pruning.
Allows you to get rid of vlans that arent' needed. You can only do this with vlan 2-1000, and done from a VTP server

One think I forgot to mention is that devices need to be setup as trunks for VTP work to work, I just wanted to make sure I mentioned that before you get carried away.