Vlan Configuration Mode Options; Vlan Configuration In Config-Vlan Mode; Vlan Configuration In Vlan Configuration Mode - Cisco Catalyst 2950 Software Configuration Manual

Configuring Normal-Range VLANs

VLAN Configuration Mode Options

You can configure normal-range VLANs (with VLAN IDs 1 to 1005) by using these two configuration
modes:
•
•

VLAN Configuration in config-vlan Mode

To access config-vlan mode, enter the vlan global configuration command with a VLAN ID. Enter a new
VLAN ID to create a VLAN or with an existing VLAN ID to modify the VLAN. You can use the default
VLAN configuration
information about commands available in this mode, refer to the vlan global configuration command
description in the Catalyst 2950 Desktop Switch Command Reference for this release. When you have
finished the configuration, you must exit config-vlan mode for the configuration to take effect. To
display the VLAN configuration, enter the show vlan privileged EXEC command.
You must use this config-vlan mode when creating extended-range VLANs (VLAN IDs greater than
1005). See the

VLAN Configuration in VLAN Configuration Mode

To access VLAN configuration mode, enter the vlan database privileged EXEC command. Then enter
the vlan command with a new VLAN ID to create a VLAN or with an existing VLAN ID to modify the
VLAN. You can use the default VLAN configuration
configure the VLAN. For more information about keywords available in this mode, refer to the vlan
VLAN configuration command description in the Catalyst 2950 Desktop Switch Command Reference for
this release. When you have finished the configuration, you must enter apply or exit for the
configuration to take effect. When you enter the exit command, it applies all commands and updates the
VLAN database. VTP messages are sent to other switches in the VTP domain, and the privileged EXEC
mode prompt appears.
Catalyst 2950 Desktop Switch Software Configuration Guide
13-8
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 64, we recommend that you configure the IEEE
802.1S Multiple STP (MSTP) on your switch to map multiple VLANs to a single STP instance. For
more information about MSTP, see
VLAN Configuration in config-vlan Mode, page 13-8
You access config-vlan mode by entering the vlan vlan-id global configuration command.
VLAN Configuration in VLAN Configuration Mode, page 13-8
You access VLAN configuration mode by entering the vlan database privileged EXEC command.
(Table 13-3) or enter multiple commands to configure the VLAN. For more
"Configuring Extended-Range VLANs" section on page
Chapter 11, "Configuring RSTP and MSTP."
(Table 13-3) or enter multiple commands to
Chapter 13 Configuring VLANs
13-14.
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