© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-1 Extending Switched Networks with Virtual LANs Introducing VLAN Operations

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-2 Outline Overview VLANs Defined VLAN Operation VLAN Membership Modes 802.1Q Trunking Inter-Switch Link Protocol and Encapsulation VLAN Trunking Protocol Features VTP Modes VTP Operations VTP Pruning Summary

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-3 VLAN = Broadcast Domain = Logical Network (Subnet) VLAN Overview Segmentation Flexibility Security

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-4 Each logical VLAN is like a separate physical bridge. VLANs can span across multiple switches. Trunks carry traffic for multiple VLANs. Trunks use special encapsulation to distinguish between different VLANs. VLAN Operation

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-5 VLAN Membership Modes

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3— Q Trunking

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-7 Importance of Native VLANs

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3— Q Frame

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-9 Per VLAN Spanning Tree +

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-10 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

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-11 ISL Encapsulation

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-12 Has 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

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-13 Cannot create, change, or delete VLANs Forwards advertisements Synchronizes Not saved in NVRAM Creates VLANs Modifies VLANs Deletes VLANs Sends and forwards advertisements Synchronizes Saved in NVRAM Creates local VLANs only Modifies local VLANs only Deletes local VLANs only Sends and forwards advertisements Does not synchronize Saved in NVRAM VTP Modes

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-14 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

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-15 Increases available bandwidth by reducing unnecessary flooded traffic Example: Station A sends broadcast, and broadcast is flooded only toward any switch with ports assigned to the red VLAN VTP Pruning

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-16 Summary A VLAN permits a group of users to share a common broadcast domain regardless of their physical location in the internetwork. VLANs improve performance and security in switched networks. In a network, a Catalyst switch operates in a network like a traditional bridge. Each VLAN configured on the switch implements address learning, forwarding and filtering decisions, and loop avoidance mechanisms. Ports belonging to a VLAN are configured with a membership mode that determines to which VLAN the ports belong. Catalyst switches support two VLAN membership modes: static and dynamic. The IEEE 802.1Q protocol is used to transport frames for multiple VLANs between switches and routers and for defining VLAN topologies.

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-17 Summary (Cont.) ISL is a Cisco proprietary protocol to transport multiple VLANs between switches and routers. ISL provides VLAN tagging capabilities while maintaining full wire-speed performance. VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the additions, deletions, and name changes of VLANs across networks. VTP operates in one of three modes: server, client, or transparent. The default VTP mode is server mode, but VLANs are not propagated over the network until a management domain name is specified or learned. VTP advertisements are sent throughout the management domain every 5 minutes or when there is a change. The configuration revision number that is included in each advertisement identifies the most current information. VTP pruning uses VLAN advertisements to determine when a trunk connection is flooding traffic needlessly.

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—2-18