t to VTP transparent. VLANs cannot be locally configured on a switch in client mode. Figure 6-2 shows a simple network with four switches. SW1 and SW2 are both VTP servers. SW3 is set to VTP transparent, and SW4 is a VTP client. Any changes to the VLAN information on SW1 will be propagated to SW2 and SW4. The changes will be passed through SW3, but will not be acted upon by that switch. Because the switch does not act on VTP updates, its VLANs must be configured manually if users on that switch are to interact with the rest of the network. VTP server VTP server VTP transparent VTP client VLAN 10 VLAN 10 VLAN 10 VLAN 10 VLAN 20 VLAN 20 VLAN 20 VLAN 30 VLAN 30 VLAN 30 VLAN 40 VLAN 40 VLAN 40 Figure 6-2. VTP modes in action Looking at Figure 6-2, it is important to understand that both VTP servers can accept and disseminate VLAN information. This leads to an interesting problem. If some- one makes a change on SW1, and someone else simultaneously makes a change on SW2, which one wins? Every time a change is made on a VTP server, the configuration is considered revised, and the configuration revision number is incremented by one. When changes are made, the server sends out VTP updates (called summary advertisements) containing the revi- sion numbers. The summary advertisements are followed by subset advertisements, which contain specific VLAN information. When a switch receives a VTP update, the first thing it does is compare the VTP domain name in the update to its own. If the domains are different, the update is ignored. If they are the same, the switch compares the update's configuration revision VLAN Trunking Protocol number to its own. If the revision number of the update is lower than or equal to the switch's own revision number, the update is ignored. If the update has a higher revi- sion number, the switch sends an advertisement request. The response to this request is another summary advertisement, followed by subset advertisements. Once it has received the subset advertisements, the switch has all the inform