Chapter 6. VLAN Trunking Protocol

In complex networks, managing VLANs can be time-consuming and error-prone. The VLAN Trunking Protocol (VTP) is a means whereby VLAN names and numbers can be managed at central devices, with the resulting configuration distributed automatically to other devices. Take, for example, the network shown in Figure 6-1. This typical three-tier network is composed completely of Layer-2 switches. There are 12 switches in all: 2 in the core, 4 in the distribution layer, and 6 in the access layer (a real network employing this design might have hundreds of switches).

Three-tier switched network

Figure 6-1. Three-tier switched network

Let’s assume the network has 10 VLANs throughout the entire design. That’s not so bad, right? Here’s what a 10-VLAN configuration might look like on a 2950:

vlan 10
 name IT
vlan 20
 name Personnel
vlan 30
 name Accounting
vlan 40
 name Warehouse1
vlan 50
 name Warehouse2
vlan 60
 name Shipping
vlan 70
 name MainOffice
vlan 80
 name Receiving
vlan 90
 name Lab
vlan 100
 name Production

Now, consider that every switch in the design needs to have information about every VLAN. To accomplish this, you’ll need to enter these commands exactly the same each time into every switch. Sure, you can copy the whole thing into a text file and paste it into each switch, but the process still won’t be fun. Look at the VLAN names. There are two warehouses, a lab, a main ...

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