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Chapter10 Understanding and Conf iguring VLANs, VTP, and VMPS
VLANs
Note VLANs support a number of parameters that are not discussed in detail in this section. For complete
information, refer to the Catalyst4500 Series Switch Cisco IOS Command Reference.
Note The VLAN configuration is stored in the vlan.dat file, which is stored in nonvolatile memory. You can
cause inconsistency in the VLAN database if you manually delete the vlan.dat file. If you want to
modify the VLAN configuration or VTP, use the commands described in the following sections and in
the Catalyst 4500S eriesSwitch Cisco IOS Command Reference.
The following sections describe how to configure VLANs:
•Configuring VLANs in Global Configuration Mode, page 10-5
•Configuring VLANs in VLAN Database Mode, page 10-7
•Assigning a Layer 2 LAN Interface to a VLAN, page 10-8
Configuring VLANs in Global Configuration Mode
If the switch is in VTP server or transparent mode (see the “Configuring VTP” section on page 27-6),
you can configure VLANs in global and VLAN configuration modes. When y ou configure VLANs in
global and config-vlan configuration modes, the VLAN configuration is saved in the vlan.dat files, not
the running-config or startup-config files. To display the VLAN configuration, enter the show vlan
command.
If the switch is in VLAN transparent mode, use the copy running-config startup-config command to
save the VLAN configuration to the startup-config file. After you save the running configuration as the
startup configuration, the show running-config and show startup-config commands display the VLAN
configuration.
Note When the switch boots, if the VTP domain name and VTP mode in the startup-config and vlan.dat files
do not match, the switch uses the configuration in the vlan.dat file.
You use the interface configuration command mode to define the port membership mode and add and
remove ports from a VLAN. The results of these commands are written to the running-config file, and
you can display the contents of the file by entering the show running-config command.
User-configured VLANs have unique IDs from 1 to 4094. To create a VLAN, enter the vlan command
with an unused ID. To verify whether a particular ID is in use, enter the show vlan id ID command. To
modify a VLAN, enter the vlan command for an existing VLAN.
See the “VLAN Default Configuration” section on page 10-4 for the list of default parameters that are
assigned when you create a VLAN. If you do not use the media keyword when specifying the VLAN
type, the VLAN is an Ethernet VLAN.