VTPv1, VTPv2
- The administrative burden of managing VLAN information increases significantly with the size of the Layer 2 network. Changing the VLAN databases on every single switch would require a lot of effort.
- Automating the propagation of VLAN information throughout the switched network was the primary motivation for the introduction of VTP.
- VTP is a proprietary protocol developed by Cisco that allows for the dynamic advertisement of VLAN attributes, including their insertion, removal, and other changes.
- Only VLANs with a regular range (VLAN IDs 1–1005) are compatible with VTP versions 1 and 2.
- Only VTPv3 supports extended range VLANs, which include VLANs 1006–4094.
- A switch can be part of only one VTP domain.
- Unless a domain advertisement is received or a domain name is configured, the switch will remain in the VTP null domain by default.
- The VLAN information is not sent across the network until the management domain name is specified or learned.
- The switch gets the VTP domain name and the revision number of the VTP setup.
- After that, advertisements with a different domain name or an earlier configuration revision number are ignored by the switch.
- Always check that the VTP configuration revision number of a new VTP clienty switch is less than the configuration revision number of all the other switches in the VTP domain before adding it to the VTP domain.
- Everything about VLANs in the VTP domain can be lost if you add a switch with a revision number higher than the revision number in the VTP domain.
- VTP revision number is stored in NVRAM and can’t be cleared even if you erase the switch configuration or even if the switch is reloaded. There are two ways to reset the VTP revision number back to zero:
- Change the VTP domain from the correct one to a dummy one and then change it back to the correct VTP domain.
- Change the switch’s VTP mode to transparent & then further change it back to server/client mode.
- On a VTP transparent switch, the revision number is always 0.
- When you reload the switches, the VTP server or client, the VLAN table and revision number will still be there because they were saved to the vlan.dat file in flash memory. By default, when a switch is in VTP transparent mode, the show running-config command will display the VLAN and VTP configurations. This is because the configuration text file stores this information.
- A VTP transparent switch’s VLANs will be removed if you erase startup-config. When using switches in either the client or server mode for VTP, the vlan.dat file will remain unaffected by the erase startup-config To wipe the VTP and VLAN information, delete the vlan.dat file and then reload the switch.
There are four more VTP roles which are as follows:
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