Exploration_LAN_Switching_Chapter3A.pdf

7/28/2019 Exploration_LAN_Switching_Chapter3A.pdf

1/31

2006 Cisco Systems, Inc. All rights reserved. Cisco Publ icITE I Chapter 6 1

VLANs

LAN Switching and Wireless Chapter 3


2/31

2006 Cisco Systems, Inc. All rights reserved. Cisco Publ icITE 1 Chapter 6 2

Objectives

Explain the role of VLANs in a converged network.

Explain the role of trunking VLANs in a converged network.

Configure VLANs on the switches in a converged networktopology.

Troubleshoot the common software or hardwaremisconfigurations associated with VLANs on switches in aconverged network topology.


3/31


VLANs in a Converged Network

Before VLANs (Virtual LANs)


4/31



Introducing VLANs


5/31



Introducing VLANs


6/31



Benefits of a VLAN


7/31 2006 Cisco Systems, Inc. All rights reserved. Cisco Publ icITE 1 Chapter 6 7


Characteristics of a VLAN




Types of VLANs: Data VLANs (user-generated traffic)

Default VLAN (VLAN 1 is the default)

Native VLAN (for untagged traffic)

Management VLAN (to provide management access)

Voice VLAN (VoIP traffic)




Data VLANs: Configured to carry only user-generated traffic

Separate from Voice and Management traffic




Default VLAN: All switch ports become a member of the Default VLAN after boot

VLAN 1 is the default VLAN

Cannot be renamed or deleted

CDP, STP and other protocols are associated to VLAN 1




Native VLAN: Handles untagged traffic (not associated to any of the VLANs)

Assigned to an 802.1Q trunk port

Native VLAN (for untagged traffic)

Provides backward compatibility with legacy LANs




Management VLAN: Allows to access management capabilities of a switch

VLAN 1 is the default Management VLAN (should be changed)




Voice VLANs Dedicated VLAN to assure enough bandwidth for voice quality

Delay of less than 150 ms across the network




Voice VLANs




VLAN port membership modes: Static VLAN (manually assigned)

Dynamic VLAN (uncommon; VLAN Membership Policy Server)

Voice VLAN




VLAN Port Membership Mode



Trunking VLANs in a Converged Network

VLAN trunk: A point-to-point link between two network devices that carries more

than one VLAN

Cisco supports IEEE 802.1Q for coordinating trunks on Fa and Gi




VLAN trunks




How to manage broadcast domains with VLANs: Where does a Bcast go with or without VLAN segmentation?




How to manage broadcast domains with VLANs: How does PC1 communicates with PC5?




How to manage broadcast domains with VLANs

Intra-VLAN communication: how does PC1 communicate with PC4? (include ARPs)Inter-VLAN communication: how does PC1 communicate with PC5? (include ARPs)




How to manage broadcast domains with VLANs Layer 3 Switch: SVI (switch virtual interface)




Benefits of VLAN trunks:

With or without VLAN trunks


25/31



How a trunk works: Tag frame before placing it in a trunk

802.1Q frame tagging

FCS is recalculated

VLAN tag field details:

EtherType: 0x8100

Tag control information (includes 12-bit VLAN ID)


26/31



Native VLANs and 802.1Q trunking: Tagged Frames on the Native VLAN:

Dropped by the switch

Devices should not tag traffic destined for the native VLAN

Untagged Frames on the Native VLAN:

Remains untagged

Are forwarded on the configured native VLAN


27/31



Native VLANs and 802.1Q trunking


28/31



How a trunk works?


29/31



How a trunk works?


30/31



How a trunk works?


31/31


How a trunk works?

Exploration_LAN_Switching_Chapter3A.pdf

Documents

Transcript of Exploration_LAN_Switching_Chapter3A.pdf