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What is VTP and how can you use it for VLAN design and scalability?

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If you work with network engineering, you probably know how important VLANs are for segmenting and securing your network traffic. But managing VLANs across multiple switches can be challenging, especially when you need to add, delete, or modify them. That's where VTP comes in handy. VTP, or VLAN Trunking Protocol, is a Cisco proprietary protocol that allows you to synchronize VLAN information among switches in the same VTP domain. In this article, you'll learn what VTP is, how it works, and how you can use it for VLAN design and scalability.

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Ehsan Momeni Bashusqeh

Network Automation Engineer & Senior Network Engineer @Sadad Informatics Corporation; NetDevOps Enthusiast
Mostafa Makwar

TIM Network Engineer at Orange Business ( CCNA || CCNP ) || PaloAlto || Fortinet || ACI || SD-WAN || F5 || Aruba…
John Gibbs

CCIE #11572, DEVASC, DevNet Class of 2020, #Init6 Member, Cisco Champion 2020-2021 and 2021-2022

1 VTP Modes

VTP has three modes of operation: server, client, and transparent. A VTP server is a switch that can create, delete, or modify VLANs and advertise them to other switches in the same VTP domain. A VTP client is a switch that receives VLAN information from a VTP server and updates its own VLAN database accordingly. A VTP client cannot create, delete, or modify VLANs locally. A VTP transparent switch is a switch that does not participate in VTP, but passes VTP messages through its trunk ports. A VTP transparent switch can create, delete, or modify VLANs locally, but does not advertise them to other switches.

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Ehsan Momeni Bashusqeh

Network Automation Engineer & Senior Network Engineer @Sadad Informatics Corporation; NetDevOps Enthusiast
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VTP transparent mode – a switch using this mode doesn’t share its VLAN database, but it forwards received VTP advertisements. You can create and delete VLANs on a VTP transparent switch, but these changes will not be sent to other switches. VTP mode off – similar to VTP transparent mode, with a difference that a switch using this mode will not forward received VTP updates. This command is supported only in VTP V3.

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Mostafa Makwar

TIM Network Engineer at Orange Business ( CCNA || CCNP ) || PaloAlto || Fortinet || ACI || SD-WAN || F5 || Aruba Clearpass || SolarWinds || Checkpoint
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VTP Modes: 1. Server Mode: ? Servers are where VLANs are created, deleted, or modified. ? The changes made on a VTP server are sent to other switches in the network. ? Servers synchronize their VLAN database with other servers and clients. 2. Client Mode: ? Clients receive and store VLAN information from VTP servers. ? They cannot create, delete, or modify VLANs, ensuring consistency in VLAN configurations across the network. 3. Transparent Mode: ? Transparent switches do not participate in VTP updates. ? They simply forward VTP messages through the network without processing them. ? VLANs can be created, deleted, or modified locally on a transparent switch, but these changes are not shared.

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Cristian Critelli

EMEA Lead Networking & Resilience Specialist Partner Solution Architect at Amazon Web Services (AWS) [ex Microsoft Azure]
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VTP (VLAN Trunking Protocol) is a Cisco-specific protocol used to manage VLAN configurations across a switched network, offering centralized management and scalability. In VTP, changes made to VLANs on a server switch are propagated to all switches in the domain, ensuring consistency and reducing configuration errors. There are three VTP modes: Server Mode, for central VLAN management; Client Mode, typically used for edge switches, which receive configurations from the server; and Transparent Mode, where switches forward VTP advertisements but manage VLANs locally. While VTP simplifies VLAN management, it requires careful implementation and security measures to prevent propagation of configuration errors across the network.

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Ehsan Momeni Bashusqeh

Network Automation Engineer & Senior Network Engineer @Sadad Informatics Corporation; NetDevOps Enthusiast
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VTP client mode – a switch using this mode can’t change its VLAN configuration. That means that a VTP client switch cannot create or delete VLANs. However, received VTP updates are processed and forwarded. VTP server mode – a switch using this mode can create and delete VLANs. A VTP server switch will propagate VLAN changes. This is the default mode for Cisco switches.

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Abdulsamad Kazeem

Network and Cloud Connectivity | Senior Network Engineer - Automation at Leaseweb Global B.V
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VTP - VLAN Trunking Protocol Is a cisco propreitary protocol used to "trunk" VLAN configuration accross multiple conmected switches. Basically, this enables all switches in the VTP domian share the same VLAN config across board. Any change made to a VLAN on a VTP master is automatically replicated on all other VTP client switches. This was saves the network admin the time & effort to carry out VLAN changes maually across multiple switches. A switch in a VTP domain can operate in 3 modes: Server : Can make VLAN changes (add, delete, update), and this will be replicated across the domain. Client : Only accepts VTP messages from the server for VLAN change. Transparent : Allows VTP messages to pass without making any change on the switch.

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2 VTP Pruning

VTP pruning is a feature that improves network efficiency by reducing unnecessary broadcast traffic on trunk links. VTP pruning works by dynamically pruning VLANs that are not needed on a trunk port, based on the VLAN membership of the switches connected to that port. For example, if a switch has no ports in VLAN 10, it does not need to receive broadcasts from VLAN 10 on its trunk port. VTP pruning can be enabled on a VTP server, and it applies to all switches in the same VTP domain.

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John Gibbs

CCIE #11572, DEVASC, DevNet Class of 2020, #Init6 Member, Cisco Champion 2020-2021 and 2021-2022
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VTP can be extremely useful if configured carefully. Best practices are to; configure switches in transparent mode, enable VTP pruning to remove unnecessary VLANs, ensure that all switches that are configured with the same VLANs are part of the same VTP domain. Configure Version 3 to benefit from more features, such as MSTP mapping, extended VLAN ranges, higher security and reliability. Configure a strong password for your VTP domain. Check your VLAN and VTP configurations regularly to ensure your VLAN schema aligns with your network architecture.

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3 VTP Version 3

VTP version 3 is an enhanced version of VTP that supports some additional features, such as extended VLAN range, private VLAN propagation, MSTP mapping, and primary server authentication. VTP version 3 also provides more security and reliability by using a hidden password, a revision number, and a device ID to prevent unauthorized or accidental changes to the VLAN database. VTP version 3 is compatible with VTP version 1 and 2, but it requires all switches in the same VTP domain to run the same VTP version.

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4 VTP Best Practices

VTP can be a useful tool for VLAN design and scalability, but it also comes with some risks and limitations. To ensure safe and effective use, it's best to use VTP only when you have a large number of switches and VLANs that need to be consistent across the network. You should also use VTP version 3, as it provides more features and security than previous versions. Additionally, you should use a unique and meaningful name for your VTP domain, and set a strong and hidden password that you regularly change. To reduce unnecessary broadcast traffic on trunk links, you should enable VTP pruning, and verify that it's working correctly. If you don't need to synchronize VLANs with other switches or if you're using unsupported VLANs such as private or voice ones, you should use transparent mode. Furthermore, when adding or removing switches from a VTP domain, make sure to check the status and revision number before and after the change. Finally, have backup and restore procedures for your VLAN database in place and test them regularly.

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5 VTP Troubleshooting

VTP can cause problems if not configured or maintained properly. To troubleshoot, check the VTP domain name, password, version, trunk status, pruning status, and mode if a switch isn't receiving or updating VLAN information from a VTP server. For incorrect or unwanted VLAN information, review the domain name, password, version, revision number, and device ID. If a switch causes a VTP database corruption or deletion, investigate the domain name, password, version, revision number, device ID and backup and restore procedures.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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What is VTP and how can you use it for VLAN design and scalability?

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1 VTP Modes

2 VTP Pruning

3 VTP Version 3

4 VTP Best Practices

5 VTP Troubleshooting

6 Here’s what else to consider

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What is VTP and how can you use it for VLAN design and scalability?

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1 VTP Modes

2 VTP Pruning

3 VTP Version 3

4 VTP Best Practices

5 VTP Troubleshooting

6 Here’s what else to consider

Network Engineering

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