ole cable out to each switch, and the whole process could take quite a while. Now, add into the equation the possibility that you'll need to add or delete a VLAN at some point, or change the name of one of them. You'll have make the rounds all over again each time there's a change to make. I can hear you thinking, "But I can just telnet to each switch to make the changes!" Yes, you can, but when you change the VLAN you're connected through without thinking, you'll be back out there working on the consoles-and this time you'll have the foreman threatening you with whatever tool he happened to find along the way because the network's been down since you mucked it up. (Don't worry, things like that almost never happen more than once.) While the telnet approach is an option, you need to be very careful about typos. Human error has to be the primary cause of outages worldwide. Fortunately, there's a better way: VTP. VTP allows VLAN configurations to be managed on a single switch. Those changes are then propagated to every switch in the VTP domain. A VTP domain is a group of connected switches with the same VTP domain string configured. Interconnected switches with differently configured VTP domains will not share VLAN information. A switch can only be in one VTP domain; the VTP domain is null by default. Chapter 6: VLAN Trunking Protocol Switches with mismatched VTP domains will not negotiate trunk protocols. If you wish to establish a trunk between switches with mis- matched VTP domains, you must have their trunk ports set to mode trunk. See Chapter 5 for more information. The main idea of VTP is that changes are made on VTP servers. These changes are then propagated to VTP clients, and any other VTP servers in the domain. Switches can be configured manually as VTP servers, VTP clients, or the third possibility, VTP transparent. A VTP transparent switch receives and forwards VTP updates, but does not update its configuration to reflect the changes they contain. Some switches default to VTP server, while others defaul