13-3
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 13 Configuring VLANs
Understanding VLANs
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 13-11.
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 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.
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