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Configuring Normal-Range VLANs
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Saving VLAN Configuration
The configurations of VLAN IDs 1 to 1005 are always saved in the VLAN database (vlan.dat file). If the
VTP mode is transparent, they are also saved in the switch running configuration file. You can enter the
copy running-config startup-config privileged EXEC command to save the configuration in the startup
configuration file. To display the VLAN configuration, enter the show vlan privileged EXEC command.
When you save VLAN and VTP information (including extended-range VLAN configuration
information) in the startup configuration file and reboot the switch, the switch configuration is selected
as follows:
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If the VLAN database configuration is used at startup and the startup configuration file contains
Caution
extended-range VLAN configuration, this information is lost when the system boots up.
Default Ethernet VLAN Configuration
Table 13-2
Catalyst 2928 Switch Software Configuration Guide
13-6
The switch supports 64 spanning-tree instances. If a switch has more active VLANs than supported
spanning-tree instances, spanning tree can be enabled on 128 VLANs and is disabled on the
remaining VLANs. If you have already used all available spanning-tree instances on a switch,
adding another VLAN anywhere in the VTP domain creates a VLAN on that switch that is not
running spanning-tree. If you have the default allowed list on the trunk ports of that switch (which
is to allow all VLANs), the new VLAN is carried on all trunk ports. Depending on the topology of
the network, this could create a loop in the new VLAN that would not be broken, particularly if there
are several adjacent switches that all have run out of spanning-tree instances. You can prevent this
possibility by setting allowed lists on the trunk ports of switches that have used up their allocation
of spanning-tree instances.
If the number of VLANs on the switch exceeds the number of supported spanning-tree instances,
we recommend that you configure the IEEE 802.1s Multiple STP (MSTP) on your switch to map
multiple VLANs to a single spanning-tree instance. For more information about MSTP, see
Chapter 17, "Configuring MSTP."
To access VLAN configuration mode, enter the vlan global configuration command with a VLAN
ID. Enter a new VLAN ID to create a VLAN, or enter an existing VLAN ID to modify that VLAN.
You can use the default VLAN configuration
the VLAN. For more information about commands available in this mode, see the vlan global
configuration command description in the command reference for this release. When you have
finished the configuration, you must exit VLAN configuration mode for the configuration to take
effect. To display the VLAN configuration, enter the show vlan privileged EXEC command.
If the VTP mode is transparent in the startup configuration, and the VLAN database and the VTP
domain name from the VLAN database matches that in the startup configuration file, the VLAN
database is ignored (cleared), and the VTP and VLAN configurations in the startup configuration
file are used. The VLAN database revision number remains unchanged in the VLAN database.
If the VTP mode or domain name in the startup configuration does not match the VLAN database,
the domain name and VTP mode and configuration for the first 1005 VLANs use the VLAN
database information.
If VTP mode is server, the domain name and VLAN configuration for the first 1005 VLANs use the
VLAN database information
shows the default configuration for Ethernet VLANs.
(Table
13-2) or enter multiple commands to configure
Chapter 13
Configuring VLANs
OL-23389-01
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Troubleshooting
