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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 17 Configuring VLANs
VLANs
• Token Ring TrCRF VLANs
For more information on configuring Token Ring VLANs, see the Catalyst 6500 Series Software
Configuration Guide.
Normal-Range VLAN Configuration Guidelines
Follow these guidelines when creating and modifying normal-range VLANs in your network:
• The switch supports 1005 VLANs in VTP client, server, and transparent modes.
• Normal-range VLANs are identified with a number between 1 and 1001. VLAN numbers 1002
through 1005 are reserved for Token Ring and FDDI VLANs.
• VLAN configuration for VLANs 1 to 1005 are always saved in the VLAN database. If the VTP mode
is transparent, VTP and VLAN configuration are also saved in the switch running configuration file.
• With VTP versions 1 and 2, the switch supports VLAN IDs 1006 through 4096 only in VTP
transparent mode (VTP disabled). These are extended-range VLANs and configuration options are
limited. Extended-range VLANs created in VTP transparent mode are not saved in the VLAN
database and are not propagated. VTP version 3 supports extended range VLAN (VLANs 1006 to
4096) database propagation. If extended VLANs are configured, you cannot convert from VTP
version 3 to version 1 or 2. See the “Creating an Extended-Range VL AN” section on page 17-18.
• Before you can create a VLAN, the switch must be in VTP server mode or VTP transparent mode.
If the switch is a VTP server, you must define a VTP domain or VTP will not function.
• The switch does not support Token Ring or FDDI media. The switch does not forward FDD I,
FDDI-Net, TrCRF, or TrBRF traffic, but it does propagate the VLAN configuration through VTP.
• The switch supports 128 spanning-tree instances. If a switch has more active VLANs than s upported
spanning-tree instances, spanning tree can be enabled on 128 V LANs and is disabled on the
remaining VLANs. If you have already used all available spanning-tree instances on a switch,
adding another VLAN anywhere in the VTP domain creates a VLAN on that switch that is not
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 o n the topology of
the network, this could create a loop in the new VLAN that would not be broken, particularl y 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 the number of supported 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 21, “Configuring MSTP.”
Default Ethernet VLAN Configuration
Note The switch supports Ethernet interfaces exclusively. Because FDDI and Token Ring VLANs are not
locally supported, you only configure FDDI and Token Ring media-specific characteristics for VTP
global advertisements to other switches.