Cisco Systems 3750E manual 13-2

Chapter 13 Configuring VLANs

Understanding VLANs

Note Before you create VLANs, you must decide whether to use VLAN Trunking Protocol (VTP) to maintain global VLAN configuration for your network. For more information on VTP, see Chapter 14, “Configuring VTP.”

Figure 13-1shows an example of VLANs segmented into logically defined networks.

Figure 13-1

Cisco router

Gigabit

Ethernet

VLANs as Logically Defined Networks

Engineering	Marketing	Accounting
VLAN	VLAN	VLAN

Floor 3

Floor 2

Floor 1

90571

VLANs are often associated with IP subnetworks. For example, all the end stations in a particular IP subnet belong to the same VLAN. Interface VLAN membership on the switch is assigned manually on an interface-by-interface basis. When you assign switch interfaces to VLANs by using this method, it is known as interface-based, or static, VLAN membership.

Traffic between VLANs must be routed or fallback bridged. The switch can route traffic between VLANs by using switch virtual interfaces (SVIs). An SVI must be explicitly configured and assigned an IP address to route traffic between VLANs. For more information, see the “Switch Virtual Interfaces” section on page 11-5and the “Configuring Layer 3 Interfaces” section on page 11-31.

Note If you plan to configure many VLANs on the switch and to not enable routing, you can use the sdm prefer vlan global configuration command to set the Switch Database Management (sdm) feature to the VLAN template, which configures system resources to support the maximum number of unicast MAC addresses. For more information on the SDM templates, see Chapter 8, “Configuring SDM Templates,” or see the sdm prefer command in the command reference for this release.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

13-2 OL-9775-02