Propagating VLAN Information with VTP
What is the VTP protocol?

Switches in a single VTP domain exchange VTP updates to distribute and synchronize VLAN information. VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the additions, deletions, and name changes of VLANs on all switches in a VTP domain.

VTP runs over trunk links between switches allowing interconnected switches to exchange layer 2 frames, synchronizing a single list of configured VLANs. This reduces the manual configuration required at each switch; VLANs can be created on one switch and then propagated to others.

These are the attributes of VTP:

  • VTP is a Cisco proprietary protocol.
  • VTP will advertise VLANs 1-1005.
  • VTP updates are exchanged only across trunk links.
  • Each switch operates in a given VTP "mode" which determines how VTP updates are sent from and received by that switch.
  • There are three VTP versions that support different features.

VTP in the Campus Infrastructure Module
There are some benefits to using VTP within the guidelines of the Campus Infrastructure module:

  • VTP domain is restricted to building switch blocks.
  • VTP keeps VLAN information consistent between Building Distribution and Building Access switches.
  • VLAN configuration errors or failures will be contained to a switch block.
  • However knowledge of all VLANs does not need to exist on all switches within the Campus Infrastructure module. Usage of VTP is optional and in high availability environments it is best practice to set all switches to ignore VTP updates.
CAUTION:

VLANs deleted on one switch may be deleted on all switches in the VTP domain and therefore all ports removed from that VLAN. Delete VLANs with caution on a switch participating in a VTP domain with other switches.


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