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VTP modes and versions : VTPv1, VTPv2 and VTPv3

This topic is basically on the VLAN trunking Protocol which is called as VTP. I am talking about this topic as i am getting a lot of queries about the VTP protocol. Some of the questions i will summarised with this article. There are some of the questions which often asked at the time of the interview and are the basic questions.

Below are the questions about the VTP.
  • So what actual VTP do ? 
  • How we manage VLANs with the VTP ?
  • What are the various versions of VTP ?
  • How they differ from each other ?
  • what is the range of the VLANs supported ?
  • What is VTP Pruning ?
  • What are VTP modes ?
  • What are the different kinds of VTP advertisements ?

I understand there might be more queries on the VTP but let's start with the general talk about the VTP first. May be with this article most of the queries will be understandable.

Fig 1.1- Sample Switched Network

So VTP is a called as Layer 2 messaging protocol that contains VLAN configuration information  by managing the addition, deletion, and renaming of VLANs within a VTP domain. A VTP domain (also called a VLAN management domain) is made up of one or more network devices that share the same VTP domain name and that are interconnected with trunks. 

With the help of VTP we can minimises misconfigurations and configuration inconsistencies that can result in a number of problems, such as duplicate VLAN names, incorrect VLAN-type specifications, and security violations. With VTP, we can make configuration changes centrally on one or more network devices and have those changes automatically communicated to all the other network devices in the network. 

So hopefully you got the point of VTP now which simply a management plane for creating, deleting and editing the VLANs in the network.

VTP Versions
VTP has three versions and these versions are VTPv1, VTPv2 and VTPv3. Let me share some of the insights which will show you the feature and the capabilities of the VTP versions.
  • VTPv1 and VTPv2 supports VLAN from 1 to 1000, while VTPv3 supports from VLAN 1 to 4096.
  • Extended-range VLANs are supported only in VTP version 3. If converting from VTP version 3 to VTP version 2, VLANs in the range 1006 to 4094 are removed from VTP control. 
  • VTP version 3 supports propagation of any database in a domain by allowing you to configure a primary and secondary server 
  • VTP version 3 is not supported on private VLAN (PVLAN) ports. 
  • Prior to configuring VTP version 3, you must ensure that the spanning-tree extend system-id command has been enabled. 
  • If there is insufficient DRAM available for use by VTP, the VTP mode changes to transparent. 
VTP Modes
There are 3 modes of VTP and these modes are :
  • VTP Server: With the configuration of VTP Server on the switch, we can create, delete and edit the VLANs with all features. VTP servers advertise their VLAN configuration to other network devices in the same VTP domain and synchronise their VLAN configuration with other network devices based on advertisements received over trunk links. VTP server is the default mode. 
  • VTP Client: VTP Client just copy the way VTP server do in the VTP domain but VTP client can't create, delete and edit VLANs in the VTP domain.
  • VTP transparent: VTP transparent network devices do not participate in VTP. A VTP transparent network device does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, a transparent network device will forward received VTP advertisements from its trunking LAN ports. In VTP version 3, a transparent network device is specific to an instance.
In my next discussion we will come with the VTP advertisements and VTP pruning in details. Please let me know if there is any other queries you have with the VTP functionality in the Switched network.