Cisco Catalyst 3560-X Series, Software Configuration Manual

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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring VLANs
Configuring Extended-Range VLANs
•
Creating an Extended-Range VLAN with an Internal VLAN ID, page 1-13
Default VLAN Configuration
See Table 1-2 on page 1-7 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
the
“Configuring VTP Mode” section on page 1-11 . 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. For more information about MSTP, see
Chapter 1, “Configuring MSTP.”
•
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.
Note
Switches running the LAN base feature set support only static routing on SVIs.
–
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 1-13 .