Configuring VTP Version 3 on Cisco Switches

GNS3 Lab

Overview

Virtual Trunking Protocol (VTP) is a Cisco-proprietary protocol that simplifies the management of VLANs across a network. By using VTP, network administrators can add, delete, and rename VLANs on a protocol-supporting switch and have those changes propagate to all other switches in the VTP domain. This article focuses on configuring VTP version 3, the latest and most secure version of the protocol, which offers enhancements over its predecessors, such as support for extended VLANs (VLANs 1006 to 4094), improved security features, and the ability to carry other database information, not just VLAN configurations.

Understanding VTP Version 3 Improvements

VTP version 3 introduces several significant improvements over version 2, including:

Enhanced Security: Provides protection against unintended database overrides during insertion of new switches and prevents unauthorized VTP updates.
Extended VLAN Support: Supports extended VLAN range (1006-4094) for database propagation.
Database Flexibility: Allows for the propagation of multiple databases, not just VLANs. This includes MST (Multiple Spanning Tree) configurations.
Primary Server Role: Introduces the concept of a primary server, where VLAN creation and modification can only be done on the primary server, providing a more controlled environment.

Prerequisites

Before configuring VTP version 3, ensure that all switches in the VTP domain are capable of supporting VTP version 3. Also, it's crucial to have a clear plan for your VTP domain, including the VLANs you intend to distribute across the network.

Configuration Steps

The following steps will guide you through configuring VTP version 3 on a Cisco switch:

Define the VTP Domain and Version

Start by defining the VTP domain. This is a common domain name that VTP switches use for VLAN information exchange. Also, set the VTP version to 3.
```
 Switch(config)# vtp domain <domain-name>
 Switch(config)# vtp version 3
```
Set VTP Mode

VTP operates in three modes: Server, Client, and Transparent. In VTP version 3, there's also an OFF mode, which disables VTP. Choose the appropriate mode for your switch. Note that in version 3, the server mode is divided into primary and secondary servers.
```
 Switch(config)# vtp mode server
```
Only the primary server can create, modify, or delete VLANs in a VTP version 3 domain. To designate a switch as the primary server for vlans:
```
 Switch# vtp primary vlan
```
Configure VTP Password (Optional, but Recommended)

VTP version 3 allows for an enhanced security mechanism that includes a hidden password option, providing more security than the plain-text password used in earlier versions.
```
 Switch(config)# vtp password <password> hidden
```
Verify Configuration

After configuring VTP settings, verify your configuration with the following command:
```
 Switch# show vtp status
```
Check the VTP version, mode, domain, and operational status to ensure everything is set as expected.

Considerations for VTP Version 3

Compatibility: VTP version 3 is not compatible with previous versions. Ensure all switches in your VTP domain support and are configured for VTP version 3.
Deployment: Be cautious when deploying or making changes to VTP configurations, as improper settings can lead to VLAN configuration issues across your network.
Security: Always use the enhanced security options available in VTP version 3 to protect against unauthorized access and configuration changes.

Conclusion

VTP version 3 offers advanced features and security enhancements, making VLAN management across your network more efficient and secure. By following the steps outlined in this guide, you can successfully configure VTP version 3 on your Cisco switches, ensuring a robust and scalable network infrastructure. Remember, proper planning and testing are crucial before deploying changes to a production environment.