© 2002, Cisco Systems, Inc. All rights reserved.
© 2002, Cisco Systems, Inc. All rights reserved. 2
Extending Switched Networks
with VLANs
Module 4
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-3
Objectives
Upon completing this module, you will be able to:
•
Use Cisco IOS commands to configure VLANs, VTP, IEEE
802.1Q trunking, and ISL trunking, given a functioning
access layer switch
•
Execute an add, move, or change on an access layer
switch, given a new network requirement
•
Use show commands to identify anomalies in VLAN, VTP,
ISL trunking, and spanning-tree operations, given an
operational access layer switch
•
Use debug commands to identify events and anomalies in
VLAN, VTP, ISL trunking, and spanning-tree operations,
given an operational access layer switch
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-4© 2002, Cisco Systems, Inc. All rights reserved. 4
VLAN Operation Overview
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-5
Objectives
Upon completing this lesson, you will be
able to:
•
Describe the features and operation of a VLAN,

Per-VLAN Spanning Tree
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-13
•
Performed with ASIC
•
Not intrusive to client
stations; ISL header not seen
by client
•
Effective between switches,
and between routers and
switches
ISL trunks enable VLANs across a backbone.
ISL Tagging
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-14
ISL Encapsulation
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-15
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A messaging system that advertises VLAN configuration information
•
Maintains VLAN configuration consistency throughout a common
administrative domain
•
Sends advertisements on trunk ports only
VTP Protocol Features
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-16
•
Forwards
advertisements
•

Saved in NVRAM
VTP Modes
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-17
•
VTP advertisements are sent as multicast frames.
•
VTP servers and clients are synchronized to the latest revision number.
•
VTP advertisements are sent every 5 minutes or when there is a change.
VTP Operation
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-18
•
Increases available bandwidth by reducing unnecessary flooded traffic
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Example: Station A sends broadcast, and broadcast is flooded only toward
any switch with ports assigned to the red VLAN
VTP Pruning
© 2002, Cisco Systems, Inc. All rights reserved. ICND v2.0—4-19
Summary
•
A VLAN permits a group of users to share a common
broadcast domain regardless of their physical location in
the internetwork. VLAN improve performance and security
in switched networks.
•
A Catalyst switch operates in a network like a traditional
bridge. Each VLAN configured on the switch implements
address learning, forwarding/filtering decisions, and loop
avoidance mechanisms.
•