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Catalyst 2960 and 2960-S Switch Software Configuration Guide
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Chapter 13 Configuring VLANs
Configuring Normal-Range VLANs
Normal-Range VLAN Configuration Guidelines
Follow these guidelines when creating and modifying normal-range VLANs in your network:
• The switch supports 255 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 4094 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
4094) database propagation. If extended VLANs are configured, you cannot convert from VTP
version 3 to version 1 or 2. See the “Configuring Extended-Range VLANs” secti on on page 13-10.
• 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 17, “Configuring MSTP.”
• When a switch in a stack learns a new VLAN or deletes or modifies an existing VLAN (either
through VTP over network ports or through the CLI), the VLAN information is communicated to all
stack members.
• When a switch joins a stack or when stacks merge, VTP information (the vlan.dat file) on the new
switches will be consistent with the stack master.
Note Stacking is supported only on Catalyst 2960-S switches running the LAN base image.
Configuring Normal-Range VLANs
You configure VLANs in vlan global configuration command by entering a VLAN ID. Enter a new
VLAN ID to create a VLAN, or enter an existing VLAN ID to modify that VLAN. You can use the
default VLAN configuration (Table 13-2) or enter multiple commands to configure the VLAN. For more
information about commands available in this mode, see the vlan global configuration command