Specifications

CHAPTER 2
VLAN Implementation
VTP works by using Configuration Revision numbers and VTP advertisements:
n All switches send out VTP advertisements every five minutes or when there is a change to the VLAN database
(when a VLAN is created, deleted, or renamed).
n VTP advertisements contain a Configuration Revision number. This number is increased by one for every VLAN
change.
n When a switch receives a VTP advertisement, it compares the Configuration Revision number against the one in its
VLAN database.
n If the new number is higher, the switch overwrites its database with the new VLAN information and forwards the
information to its neighbor switches.
n If the number is the same, the switch ignores the advertisement.
n If the new number is lower, the switch replies with the more up-to-date information contained in its own database.
VTP Switch Roles
A switch can be a VTP:
n Server: The default VTP role. Servers can create, delete, and rename VLANs. They originate both periodic and trig-
gered VTP advertisements and synchronize their databases with other switches in the domain.
n Client: Clients cannot make VLAN changes. They originate periodic VTP advertisements and synchronize their
databases with other switches in the domain.
n Transparent: It can create, delete, and rename VLANs, but its VLANs are only local. It does not originate adver-
tisements or synchronize its database with any other switches. It forwards VTP advertisements out its trunk links,
however.
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue