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Configuring VLANs

Finding Feature Information

Your software release may not support all the features documented in this chapter. For the latest feature
information and caveats, see the release notes for your platform and software release.
Use Cisco Feature Navigator to find information about platform support an d Cisco software image
support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on
Cisco.com is not required.

Information About Configuring VLANs

VLANs

A VLAN is a switched network that is logically segmented by function, project team, or application,
without regard to the physical locations of the users. VLANs have the same attributes as physical LANs,
but you can group end stations even if they are not physically located on the same LAN segment. Any
switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and
flooded only to end stations in the VLAN. Each VLAN is considered a logical network, and packets
destined for stations that do not belong to the VLAN must be forwarded through a router or a switch
supporting fallback bridging, as shown in Figure 17-1. Because a VLAN is considered a separate logical
network, it contains its own bridge Management Information Base (MIB) information and can support
its own implementation of spanning tree. See Chapter 20, “Configuring STP.
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 18,
“Configuring VTP.”