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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
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Chapter 9 Configuring VLANs
Configuring VLANs
Assigning a Layer 2 LAN Interface to a VLAN
A VLAN created in a management domain remains unused until you assign one or more LAN ports to
the VLAN.
Note Make sure you assign LAN ports to a VLAN of the appropriate type. Assign Ethernet ports to
Ethernet-type VLANs.
To assign one or more LAN ports to a VLAN, complete the procedures in the “Configuring LAN
Interfaces for Layer 2 Switching” section on page 7-7.
Configuring the Internal VLAN Allocation Policy
Internal VLAN allocation policy is supported in Release 12.1(13)E and later releases. For more
information about VLAN allocation, see the “VLAN Ranges” section on page 9-2.
Note The internal VLAN allocation policy is applied only following a reload.
To configure the internal VLAN allocation policy, perform this task:
When you configure the internal VLAN allocation policy, note the following syntax information:
Enter the ascending keyword to allocate internal VLANs from 1006 and up.
Enter the descending keyword to allocate internal VLAN from 4094 and down.
This example shows how to configure descending as the internal VLAN allocation policy:
Router# configure terminal
Router(config)# vlan internal allocation policy descending
Mapping 802.1Q VLANs to ISL VLANs
The valid range of user-configurable ISL VLANs is 1 through 1001 and 1006 through 4094. The valid
range of VLANs specified in the IEEE 802.1Q standard is 1 to 4094. You can map 802.1Q VLAN
numbers to ISL VLAN numbers.
Command Purpose
Step 1 Router(config)# vlan internal allocation policy
{ascending | descending}
Configures the internal VLAN allocation policy.
Router(config)# no vlan internal allocation
policy
Returns to the default (ascending).
Step 2 Router(config)# end Exits configuration mode.
Step 3 Router# reload Applies the new internal VLAN allocation policy.
Caution You do not need to enter the reload command
immediately. Enter the reload command
during a planned maintenance window.