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Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
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Chapter 13 Configuring VLANs
Configuring Extended-Range VLANs
•
STP is enabled by default on extended-range VLANs, but you can disable it by using the
no
spanning-tree vlan
vlan-id
global configuration command. When the maximum number of
spanning-tree instances are on the switch, spanning tree is disabled on any newly created VLANs.
If the number of VLANs on the switch exceeds the maximum number of 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 19, “Configuring MSTP.”
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Each routed port on the switch creates an internal VLAN for its use. These internal VLANs use
extended-range VLAN numbers, and the internal VLAN ID cannot be used for an extended-range
VLAN. If you try to create an extended-range VLAN with a VLAN ID that is already allocated as
an internal VLAN, an error message is generated, and the command is rejected.
–
Because internal VLAN IDs are in the lower part of the extended range, we recommend that you
create extended-range VLANs beginning from the highest number (4094) and moving to the
lowest (1006) to reduce the possibility of using an internal VLAN ID.
–
Before configuring extended-range VLANs, enter the
show vlan internal usage
privileged
EXEC command to see which VLANs have been allocated as internal VLANs.
–
If necessary, you can shut down the routed port assigned to the internal VLAN, which frees up
the internal VLAN, and then create the extended-range VLAN and re-enable the port, which
then uses another VLAN as its internal VLAN. See the
“Creating an Extended-Range VLAN
with an Internal VLAN ID” section on page 13-13
•
Although the switch or switch stack supports a total of 1005 (normal-range and extended-range)
VLANs, the number of routed ports, SVIs, and other configured features affects the use of the switch
hardware. If you try to create an extended-range VLAN and there are not enough hardware resources
available, an error message is generated, and the extended-range VLAN is rejected.
•
In a switch stack, the whole stack uses the same running configuration and saved configuration, and
extended-range VLAN information is shared across the stack.
Creating an Extended-Range VLAN
You create an extended-range VLAN in global configuration mode by entering the
vlan
global
configuration command with a VLAN ID from 1006 to 4094. This command accesses the VLAN
configuration mode. The extended-range VLAN has the default Ethernet VLAN characteristics (see
) and the MTU size, private VLAN, and RSPAN configuration are the only parameters you
can change. See the description of the
vlan
global configuration command in the command reference for
the default settings of all parameters. In VTP version 1 or 2, if you enter an extended-range VLAN ID
when the switch is not in VTP transparent mode, an error message is generated when you exit VLAN
configuration mode, and the extended-range VLAN is not created.
Extended-range VLANs are not saved in the VLAN database; they are saved in the switch running
configuration file. You can save the extended-range VLAN configuration in the switch startup
configuration file by using the
copy running-config startup-config
privileged EXEC command.
Note
Before you create an extended-range VLAN, you can verify that the VLAN ID is not used internally by
entering the
show vlan internal usage
privileged EXEC command. If the VLAN ID is used internally
and you want to free it up, go to the
“Creating an Extended-Range VLAN with an Internal VLAN ID”
before creating the extended-range VLAN.