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13-3
Catalyst 3750 Switch Software Configuration Guide
OL-8550-09
Chapter 13 Configuring VLANs
Understanding VLANs
VLAN range (VLANs 1 to 4094). Extended range VLANs (VLANs 1006 to 4094) are supported only in
VTP version 3. You cannot convert from VTP version 3 to VTP version 2 if extended VLANs are
configured in the domain.
Although the 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 13-10.
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 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.
Dynamic access A dynamic-access port can belong to one VLAN
(VLAN ID 1 to 4094) and is dynamically assigned by
a VMPS. The VMPS can be a Catalyst 5000 or
Catalyst 6500 series switch, for example, but never a
Catalyst 3750 switch. The Catalyst 3750 switch is a
VMPS client.
You can have dynamic-access ports and trunk ports
on the same switch, but you must connect the
dynamic-access port to an end station or hub and not
to another switch.
For configuration information, see the “Configuring
Dynamic-Access Ports on VMPS Clients” section on
page 13-31.
VTP is required.
Configure the VMPS and the client with the
same VTP domain name.
To participate in VTP, at least one trunk port
on the switch stack must be connected to a
trunk port of a second switch or switch
stack.