VTP revision number
The VTP revision number is a 32 bit value found in a field of the header of a VTP advertisement. Initially, its value is zero. The revision number is incremented by one every time there is a change in the VLAN configuration on a VTP server. A VTP client will ignore any VTP updates that have a revision number equal to or smaller than their current revision number.
A VTP revision number cannot be arbitrarily set, but it can be reset to zero.