4.6 VLAN Trunking Protocol (VTP)
4.6.4 Adding a switch to a VTP domain

Use caution when inserting a new switch into an existing domain. In order to prepare a switch to enter an existing VTP domain, perform the following steps:

  1. Issue a clear config all or erase startup-config command to remove the existing configuration. This will not clear the VTP configuration revision number. Clearing the revision number is done only by power cycling the switch.
  2. Power cycle the switch to clear the VTP nonvolatile RAM (NVRAM). This will reset the configuration revision number to 0. This ensures that the new switch will not propagate incorrect information across the domain.
  3. Determine the VTP mode of operation of the switch and include the mode when setting the VTP domain information on the switch using the show vtp status or show vtp domain command. The default for most switches is server mode. If you leave the switch in server mode, be sure to verify that the configuration revision number is set to 0 before adding the switch to the VTP domain. It is generally recommended that you have several servers in the domain, with all other switches set to client mode for purposes of controlling VTP information.
  4. It is also highly recommended that you use secure mode in your VTP domain. Assigning a password to the domain will accomplish this. This will prevent unauthorized switches from participating in the VTP domain. Use the vtp password password or the set vtp passwd passwd commands.
Lab Activity 
  In this lab activity, you will learn how to configure a VLAN trunk between a Catalyst 4000 and Catalyst 2900 switch.