CHAPTER
8-1
Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
8
Configuring VLANs
This chapter provides information about configuring virtual LANs (VLANs). It includes command-line
interface (CLI) procedures for using commands that have been specifically created or changed for the
Catalyst 2950 switches. For complete syntax and usage information for the commands used in this
chapter, refer to the Catalyst 2950 Desktop Switch Command Reference.
Note Certain port features can conflict with one another. Review the “Avoiding Configuration Conflicts”
sectiononpage14-1before you change the port settings.
This chapter does not repeat the concepts and CLI procedures provided in the standard Cisco IOS
Release 12.1 documentation. For information about the standard IOS Release 12.1 commands, refer to
the IOS documentation set available from the Cisco.com home page at Service and Support >
Technical Documents
. On the Cisco Product Documentation home page, select Release 12.1 from the Cisco
IOS Software drop-down list.
For information about configuring these settings from Cluster Management Suite (CMS), refer to the
online help.
Note Some features can be implemented only by using the CLI.
Overview
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. Any switch port can belong to a VLAN, and unicast,
broadcast, and multicast packets are forwarded and flooded only to 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 bridge as shown in Figure 8-1. VLANs are identified with a number
from 1 to 1001.
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 the Spanning Tree
Protocol (STP). For information about managing VLAN STP instances, see the “Supported STP
Instances” sectiononpage9-2.