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Configuring VLANs
VLANs
Extended-Range VLANs
With VTP version 1 and version 2, when the switch is in VTP transparent mode (VTP disabled), you can create
extended-range VLANs (in the range 1006 to 4096). VTP version supports extended-range VLANs in server or
transparent move. Extended-range VLANs enable service providers to extend their infrastructure to a greater number of
customers. The extended-range VLAN IDs are allowed for any switchport commands that allow VLAN IDs.
With VTP version 1 or 2, extended-range VLAN configurations are not stored in the VLAN database, but because VTP
mode is transparent, they are stored in the switch running configuration file, and you can save the configuration in the
startup configuration file by using the copy running-config startup-config privileged EXEC command. Extended-range
VLANs created in VTP version 3 are stored in the VLAN database.
Default VLAN Configuration
See Table 34 on page 276 for the default configuration for Ethernet VLANs. You can change only the MTU size, private
VLAN, and the remote SPAN configuration state on extended-range VLANs; all other characteristics must remain at the
default state.
Extended-Range VLAN Configuration Guidelines
Follow these guidelines when creating extended-range VLANs:
VLAN IDs in the extended range are not saved in the VLAN database and are not recognized by VTP unless the switch
is running VTP version 3.
You cannot include extended-range VLANs in the pruning eligible range.
In VTP version 1 and 2, a switch must be in VTP transparent mode when you create extended-range VLANs. If VTP
mode is server or client, an error message is generated, and the extended-range VLAN is rejected. VTP version 3
supports extended VLANs in server and transparent modes.
For VTP version 1 or 2, you can set the VTP mode to transparent in global configuration mode. See Adding a VTP
Client Switch to a VTP Domain, page 303. You should save this configuration to the startup configuration so that the
switch boots up in VTP transparent mode. Otherwise, you lose the extended-range VLAN configuration if the switch
resets. If you create extended-range VLANs in VTP version 3, you cannot convert to VTP version 1 or 2.
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.
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 (4096) 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 Creating an Extended-Range VLAN with an Internal VLAN ID, page 286.
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