Understanding VLAN Trunk Protocol (VTP)

Posted: 12th June 2022 by ccna7guru in ITN
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Understanding VTP VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations and configuration inconsistencies that can result in a number of problems, such as duplicate VLAN names, incorrect VLAN-type specifications, and security violations.

 You can use VTP to manage VLANs 1-1005 in your network. (VTP version 1 and VTP version 2 do not support VLANs 1025-4094.) With VTP, you can make configuration changes centrally on one switch and have those changes automatically communicated to all the other switches in the network.

These sections describe how VTP works:

 •Understanding the VTP Domain A VTP domain (also called a VLAN management domain) is made up of one or more interconnected switches that share the same VTP domain name. A switch can be configured to be in one and only one VTP domain. You make global VLAN configuration changes for the domain using either the command-line interface (CLI) or Simple Network Management Protocol (SNMP).

 •Understanding VTP Modes You can configure a switch to operate in any one of these VTP modes:

Server—In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP servers advertise their VLAN configuration to other switches in the same VTP domain and synchronize their VLAN configuration with other switches based on advertisements received over trunk links. VTP server is the default mode.

 •Client—VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.

 •Transparent—VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, transparent switches do forward VTP advertisements that they receive out their trunk ports.

 •Off—In the three modes described above, VTP advertisements are received and transmitted as soon as the switch enters the management domain state. In the VTP off mode, the switch behaves the same as in VTP transparent mode with the exception that VTP advertisements are not forwarded.

 •Understanding VTP Advertisements Each switch in the VTP domain sends periodic advertisements out each trunk port to a reserved multicast address. VTP advertisements are received by neighboring switches, which update their VTP and VLAN configurations as necessary.

 The following global configuration information is distributed in VTP advertisements:

•VLAN IDs (ISL and 802.1Q)                      
•Emulated LAN names (for ATM LANE) 
•802.10 SAID values (FDDI)                      
•VTP domain name                       
•VTP configuration revision number 
•VLAN configuration, including the maximum transmission unit (MTU) size for each VLAN
•Frame format                                            
•Understanding VTP Version 2      
•Understanding VTP Pruning

Understanding VLAN Trunk Protocol (VTP) – Cisco