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www.ciscopress.comCopyright 2003

CCNA 3 Chapter 9

Virtual LANs

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Objectives

• VLAN concepts

• VLAN configuration

• Troubleshooting VLANs


VLANs


VLANs

VLANs logically segment switched networks based on an organization's functions, project teams, or applications as opposed to a physical or geographical basis.


Broadcast Domains with VLANs and Routers


Broadcast Domains


Static VLANs


Dynamic VLANs


Port-Centric VLANs


VLAN Configuration


Benefits of VLANs

• Easily move workstations on the LAN• Easily add workstations to the LAN• Easily change the LAN configuration• Easily control network traffic• Improve security


VLAN Types


VLAN Tagging


Communicating Between VLANs


VLAN Configuration


Concurrent Transmission


End-to-End VLANs


Static VLANs

• Moves are controlled and managed. • There is robust VLAN management software

to configure the ports. • It is not desirable to assume the additional

overhead required when maintaining end-station MAC addresses and custom filtering tables.


Verifying VLAN Configuration


Saving a VLAN Configuration

Back up using the copy running-config tftp command, or you can use the HyperTerminal Capture Text feature to store the configuration settings.


Deleting VLANs


Troubleshooting VLANs


VLAN Problem Isolation


Problem Isolation in Catalyst Networks


Preventing Broadcast Storms


Troubleshooting VLANs


Keyword Syntax


The show Commands


VLAN Troubleshooting Scenarios

Cannot establish a trunk link between a switch and a router



VTP is not properly propagating VLAN configuration changes.



Dropped packets and loops

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