Configuring VTP/VLAN/Trunk
Figure 4-8 illustrates
multiple switches across the campus network. IEEE 802.1Q is used for trunking
method. VLANs 2 and 3 are configured as well. VTP is used to propagate the VLAN
information to the rest of the switches.
The first thing to do is define the VTP domain, which allows
VTP to manage switches that are under its domain. This command is programmed on
all four switches:
set vtp domain cisco
VTP domain names and passwords are case sensitive. A VTP domain
name is only required for server/client mode. By default, Cisco switches will
operate in server mode. For redundancy purposes, the recommendation is to have
multiple VTP servers in the switch network. Therefore, only Switch2 and Switch3
will be configured for client mode. Switch1 and Switch4 will operate in server
mode so that they may provide redundancy. Use the following command to change
Switch2 and Switch3 to client mode:
set vtp mode client
If a VTP domain name is not configured for server/client mode,
or if the switch is not programmed to be in transparent mode, any VLANs created
will be in inactive state.
The next step is to create VLANs 2 and 3. The set vlan command is used to create VLAN 3 on
Switch1:
set vlan 3
Host1 is connected to port 10/3 and is configured to be a
member of VLAN 3:
set vlan 3 10/3
By default, all ports are configured with VLAN 1. Hence, any
trunks created will have their native VLAN as VLAN 1. Port 1/2 of Switch1 will
be used to form a trunk with Switch2 so that Switch1 can pass VTP information to
Switch2. The following command will force the native VLAN for trunk 1/2 to be
VLAN 2:
set vlan 2 1/2
Typically, it is recommended to assign native VLANs rather than
using VLAN 1. The "Understanding VLAN 1" section of this
chapter provides greater insight as to why this is necessary.
The port is configured to be an IEEE 802.1Q trunk port with the
next command. Dot1q is the equivalent of IEEE 802.1Q on Cisco switches:
set trunk 1/2 dot1q
Recall from earlier discussions of trunking that trunking mode
must also be configured. The recommended method is to set trunking mode to
desirable:
set trunk 1/2 desirable
Port 1/2 will attempt to actively form a trunk with its
directly connected link because it has the desirable parameter configured. Port
10/27 will similarly be configured to form a trunk to Switch4. | 
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