Once the VLAN Trunking Protocol (VTP) is configured on the switches, the switches start advertising VLAN Trunking Protocol (VTP) information between them on their trunk ports. The main information which the switches advertise are management VTP Domain name , configuration revision number and the configured VLANs. VTP advertisements are sent as multicast Ethernet frames and all neighbor devices receive the Ethernet frames.
Three types of VLAN Trunking Protocol (VTP) advertisement messages are
• Client advertisement request: A client advertisement request message is a VTP message which a client generates for VLAN information to a server. Servers respond with both summary and subset advertisements.
• Summary advertisement: Summary advertisements are sent out every 300 seconds (5 minutes) by default or when a configuration change occurs, which is the summarized VLAN information.
• Subset advertisement: Subset advertisements are sent when a configuration change takes place on the server switch. Subset advertisements are VLAN specific and contain details about each VLAN.