VTP Advertisements

VTP uses various types of messages or advertisements to allow VTP enabled switches to exchange VLAN information. These advertisements fall into the following categories:

• Summary Advertisements
  • These contain the VTP domain name, the current revision number and other VTP configuration details
  • Summary advertisements are sent:
    • every 5 minutes by a VTP server or client to inform neighboring VTP enabled switches of the current VTP configuration revision number for its VTP domain
    • Immediately after a configuration has been made
• Subset Advertisements
  • A subset advertisement contains VLAN information
  • Subset advertisements are sent whenever
    • a VLAN is created or deleted
    • a VLAN is activated or suspended
    • the name of a VLAN is changed
    • the MTU of a VLAN is changed
    • a switch receives a request advertisement message
• Request Advertisements
  • When a request advertisement is sent to a VTP server in the same VTP domain, the VTP server responds by sending a summary advertisement and then a subset advertisement
  • Request advertisements are sent when
    • The VTP domain name has been changed
    • The switch receives a summary advertisement with a higher configuration revision number than its own
    • A subset advertisement message is missed for some reason
    • The switch has been reset