VTP vs DTP | Difference between VTP and DTP

This page compares VTP (VLAN Trunking Protocol) vs DTP (Dynamic Trunking Protocol) and mentions difference between VTP (VLAN Trunking Protocol) and DTP (Dynamic Trunking Protocol).

VTP-VLAN Trunking Protocol

VTP, VLAN Trunking Protocol

Function: As mentioned VTP stands for VLAN Trunking Protocol. As the name suggests it propagates VLAN definition to whole of the LAN. To accomplish this task, VTP protocol carriers VLAN information to all the switches available in the VTP domain.

VLAN packet in VTP mode is transmitted in ISL (Inter-Switch Link) frames or 802.1Q compliant frames. We know that a trunk is physical and logical connection between two switches across which network traffic travels or flows. In VLAN, responsibilities of trunk line is to function as conduit for VLANs between switches and routers as well between switches and other switches.

• VTP domain refers to one or more interconnected switches. It is formed so that VLAN configuration details can be shared easily.
• VTP Advertisements are used to distribute and synchronize VLAN configuration across the VTP domain.

VTP Modes

Following are the three VTP modes in which any switch can be configured:
• VTP Server:
-Advertise the VLAN information across the domain
-Create, delete, modify
• VTP Client:
-Stores the VLAN information from the server
-Can not create, delete, modify
• VTP Transparent:
-Forwards VTP advertisements
-Do not participate in VTP

Following are the features of VLAN Trunking Protocol (VTP):
• VTP protocol is used between switches.
• VLAN configuration is done on one switch (i.e. switch in VTP server mode).
• The VTP protocol automatically propagates VLAN information to all the switches in the domain i.e. switches with VTP client modes.

EXAMPLE: Suppose you have a office with 6 floors and a switch is assigned or configured on each floors. There is VLAN configuration on each floor. Suppose it has been decided to add new department to the configuration. Without VTP protocol, system admin need to go to each of the floors and need to add new department information to switches on all the six floors. It is easy to manage manually for the office having less floors and less number of departments/users. It will become cumbersome and time consuming task to manage large number of floors. Here VTP comes in to picture.

With VTP protocol, system admin need to just provide information to master switch (i.e. switch in VTP server mode) and rest of the switches will get the information automatically via VTP advertisements.

Benefits or Advantages of VLAN Trunking Protocol

Following are the advantages of VLAN Trunking Protocol (VTP) :
• VLAN configuration remains consistent across the entire VTP domain.
• VLANs are easily trunked over mixed medium e.g. ethernet VLAN is mapped to high speed ATM LANE or FDDI VLAN.
• It allows accurate monitoring and control of VLANs.
• It allows dynamic reporting of added VLANs in the network.
• Addition of new VLANs follow simple "Plug and Play" configuration.

DTP-Dynamic Trunking Protocol

As mentioned DTP stands for Dynamic Trunking Protocol. Following are the features of DTP.
• Cisco proprietary protocol. Switches from other vendors do not support DTP.
• Automatically enabled on a switch port when certain trunking modes are configured on the switch port.
• DTP manages trunk negotiation only if the port on the other switch is configured in a trunk mode that supports DTP.
• DTP supports both ISL and 802.1Q trunks.
• Some Cisco switches and routers mostly having older versions do not support DTP.

DTP-Dynamic Trunking Protocol Modes

Following are the DTP modes supported.
• On (default): (switchport mode trunk)
-Periodically sends DTP advertisements, to the remote port that it is dynamically changing to a trunking state.
• Dynamic Auto: (switchport mode dynamic auto)
-The switch port periodically sends DTP frames to the remote port. It advertises to the remote switch port that it is able to trunk but does not request to go to the trunking state.
• Dynamic Desirable: (switchport mode dynamic desirable)
-DTP frames are sent periodically to the remote port. It advertises to the remote switch port that it is able to trunk and asks the remote switch port to go to the trunking state.
• Turn off DTP: (switchport nonegogiate)
-The local port does not send out DTP frames to the remote port.
-The local port is then considered to be in an unconditional trunking state.
-Use this feature when you need to configure

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