Configuring Normal-Range Vlans; Default Ethernet Vlan Configuration - Cisco Catalyst 2975 Software Configuration Manual

Configuring Normal-Range VLANs

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Configuring Normal-Range VLANs

You configure VLANs in vlan global configuration command by entering 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
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.
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. In a switch stack, the whole stack uses the same vlan.dat file and running
configuration. 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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Default Ethernet VLAN Configuration

Table 13-2
Catalyst 2975 Switch Software Configuration Guide
13-6
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."
When a switch in a stack learns a new VLAN or deletes or modifies an existing VLAN (either
through VTP over network ports or through the CLI), the VLAN information is communicated to
all stack members.
When a switch joins a stack or when stacks merge, VTP information (the vlan.dat file) on the new
switches will be consistent with the stack master.
(Table
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.
In VTP versions 1 and 2, if VTP mode is server, the domain name and VLAN configuration for only
the first 1005 VLANs use the VLAN database information. VTP version 3 also supports VLANs
1006 to 4094.
shows the default configuration for Ethernet VLANs.
13-2) or enter multiple commands to configure the VLAN. For more
Chapter 13 Configuring VLANs
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