What is 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.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.
By default, the switch is in VTP server mode and is in the no-management domain state until the switch receives an advertisement for a domain over a trunk link or you configure a management domain. You cannot create or modify VLANs on a VTP server until the management domain name is specified or learned.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and the VTP configuration revision number. The switch ignores advertisements with a different management domain name or an earlier configuration revision number.
If you configure the switch as VTP transparent, you can create and modify VLANs but the changes affect only the individual switch.
When you make a change to the VLAN configuration on a VTP server, the change is propagated to all switches in the VTP domain. VTP advertisements are transmitted out all trunk connections.
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)
- VTP domain name
- VTP configuration revision number
- VLAN configuration, including the maximum transmission unit (MTU) size for each VLAN
|
|
|
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, switches behave the same as in VTP transparent mode with the exception that VTP advertisements are not forwarded.
Understanding VTP Version 2
If you use VTP in your network, you must decide whether to use VTP version 1 or version 2.
VTP Default Configuration:
- VTP domain name : Null
- VTP mode : Server
- VTP version 2 : disabled
- VTP password : None
- VTP pruning : Disabled
Expample configuration VTP
Configuring VTP:
router#config T
router(config)#
! configuring VTP password
router(config)# vtp password {password}
! configuring vtp mode
router(config)# vtp mode {client | server | transparent}
! configuring vtp V2
router(config)# vtp version 2
! configuring vtp pruning
router(config)# vtp pruning
The VTP configuration can be verified by the following commands:
- Show vtp status
- Show vtp counter
ref. www.cisco.com
|
