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13-3
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter 13 Configuring VLANs
Understanding VLANs
Supported VLANs
The switch supports VLANs in VTP client, server, and transparent modes. VLANs are identified by a
number from 1 to 4094. VLAN IDs 1002 through 1005 are reserved for Token Ring and FDDI VLANs.
VTP only learns normal-range VLANs, with VLAN IDs 1 to 1005; VLAN IDs greater than 1005 are
extended-range VLANs and are not stored in the VLAN database. The switch must be in VTP
transparent mode when you create VLAN IDs from 1006 to 4094.
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.
The switch supports per-VLAN spanning-tree plus (PVST+) or rapid PVST+ with a maximum of 128
spanning-tree instances. One spanning-tree instance is allowed per VLAN. See the “Normal-Range
VLAN Configuration Guidelines” section on page 13-6 for more information about the number of
spanning-tree instances and the number of VLANs. The switch supports both Inter-Switch Link (ISL)
and IEEE 802.1Q trunking methods for sending VLAN traffic over Ethernet ports.
VLAN Port Membership Modes
You configure a port to belong to a VLAN by assigning a membership mode that specifies the kind of
traffic the port carries and the number of VLANs to which it can belong. Table 13-1 lists the membership
modes and membership and VTP characteristics.
Table 13-1 Port Membership Modes and Characteristics
Membership Mode VLAN Membership Characteristics VTP Characteristics
Static-access A static-access port can belong to one VLAN and is
manually assigned to that VLAN.
For more information, see the “Assigning Static-Access
Ports to a VLAN” section on page 13-11.
VTP is not required. If you do not want VTP
to globally propagate information, set the
VTP mode to transparent. To participate in
VTP, there must be at least one trunk port on
the switch or the switch stack connected to
a trunk port of a second switch or switch
stack.
Trunk (ISL or
IEEE 802.1Q)
A trunk port is a member of all VLANs by default,
including extended-range VLANs, but membership can
be limited by configuring the allowed-VLAN list. You
can also modify the pruning-eligible list to block flooded
traffic to VLANs on trunk ports that are included in the
list.
For information about configuring trunk ports, see the
“Configuring an Ethernet Interface as a Trunk Port”
section on page 13-19.
VTP is recommended but not required. VTP
maintains VLAN configuration consistency
by managing the addition, deletion, and
renaming of VLANs on a network-wide
basis. VTP exchanges VLAN configuration
messages with other switches over trunk
links.