CCNA CHAPTER 14 BY jetarvind kumar madhukar

Release 16/07/2009 Jetking Infotrain Ltd.

Virtual LAN

Chapter 14


Chapter Objectives

Explain Virtual LAN Explain VLAN trunking Explain VLAN trunking protocol Configure and Troubleshooting VLAN


Recall - I

LAN switching increases the bandwidth of the network, which helps to solve the problem of network traffic

Spanning Tree Protocol (STP) is used to stop the network loop that occurs for an indefinite period on the layer 2 network

The Cisco Catalyst 1900 series switches are available in two editions Standard Edition and Enterprise Editions


Recall - II

The 1900 series switches automatically copies any changes made in the configuration into the NVRAM. In the 1900 switches, any changes made to the running configuration using the mode is automatically updated in the NVRAM config file

The Standard version of Catalyst 2900 provides VLAN capability

The 2900 series switches come with four and eight megabytes of memory size


Virtual LAN (VLAN)

A VLAN is a group of network devices that behave as they are connected to a single network segment


VLAN Advantages

Broadcast Control - This helps in reducing the bandwidth consumption in the network

Security - VLANs allow you to efficiently control the switch ports, which prevent unauthorized access of the network by the use of a switch port

Flexibility and Scalability - VLAN are considered as flexible because it allows you to construct groups or networks connected to a switch or a group of switches


VLAN Membership

VLAN membership can be defined as the association of the devices in a VLAN and how the devices are configured in the VLAN

The two types of VLAN membership include: Static VLANs Dynamic VLANs


VLAN Trunking When a particular VLAN switch sends a broadcast

message to another switch on the network, the receiving switch needs to identify the source of the message. This is achieved by VLAN trunking

VLAN trunking adds a tag to each data frame that is transferred from the switch


The Inter-Switch Link protocol allows tagging of the data frame before transferring it to a VLAN

The ISL encapsulates the original by placing the original Ethernet frame between the 26-byte header and the 4-byte CRC trailer frame

Inter-Switch Link (ISL) Protocol


802.1Q

The 802.1Q modifies the original frame by adding a 4 byte field called the tag field in the middle of the original Ethernet frame


Trunking

Trunking is used to communicate when the two or more hosts are connected to a different switch and belong to the same VLAN

Before configuring the ports, you must know the network structure


Inter-VLAN Routing Router Interfaces Connected to the Access Link

Router Interface Connected to the Switch


VLAN Trunking Protocol (VTP) VLAN Trunking Protocol (VTP) allows you to share

information about VLAN configuration over the network switches

VTP allows to add a new VLAN to the switch and propagate this information through the VTP messages to all other switches in layer 2 network causing them to add the new VLAN

VTP propagates information as VTP messages using trunk connections


VTP Modes

VTP modes decide the flexibility with which changes are incorporated in the network

The three VTP modes include: Server Mode Transparent Mode Client Mode


VTP Prunning VTP pruning is Cisco VTP feature that allows your

switches to dynamically delete or add VLANs to a trunk resulting in a more efficient switching network

The VTP pruning helps the switch to prevent broadcast and unicasts from flowing into switches that do not have ports in that VLAN


Case Study

The Gujarat branch of the Blue Diamond Steel Company has hired new employees for Finance, Marketing, Human Resource and Business Development departments. This made the management to expand their office premises. The new employees are placed in the new premises. The network administrator has already configured VLANs for every department and now has to assign the VLANs to the new hosts, so that the new employees can access the data of their department from the new premises.


Problem

The network administrator is unable to assign the VLANs automatically to the hosts connected and

assigning VLANs to each host manually is a tedious task


Suggested Solution

The network administrator needs to configure VTP on the new network switch and the switch to which the new network switch will be connected. He needs to enable trunking between the VLANs. In addition, he

needs to assign the VLANs to the same domain


Summary - I

Virtual Local Area Network (VLAN) is a collection of networking devices in the same broadcast domain

In order to work with a VLAN, you require a layer of 2 switches that supports them

Each VLAN created on a switch is a separate network Network broadcast, by default, are filtered from all

ports on a switch that are not members of the same VLAN

VLANs help to isolate network segments between each other


Summary - II

In VLAN trunking, the switches tag each frame sent between switches so that the receiving switch knows what to what VLAN frame belongs

With trunking you can support multiple VLANs that have on more than one switch

Cisco supports two different trunking protocols; Inter-Switch (ISL) and IEEE 802.1Q, both provide basic trunking

The ISL can be used only between two Cisco switches


Summary - III

The ISL is a proprietary tagging method that the Cisco developed to use for Ethernet and Token ring connections

The ISL header VLAN fields provide a place to encode the VLAN number

ISL is used only on Ethernet connection The ISL adds a 26-byte header and 4-byte trailer to

the original Ethernet frame The ISL is slowly being replaced in Cisco’s products

with IEEE’s 802.1Q trunking standard


Summary - IV

The 802.1Q allows trunks between different vendor’s devices, whereas ISL provided only trunking between some of the Cisco devices

Cisco 2950 switches use a slightly different configuration mode to configure VLAN and VTP information as compared to other switch configuration commands

In VLAN configuration mode, you can configure VLAN information as VTP settings. By default, a 2950 switch uses VTP server mode, so any VLANs you configure are advertised in VTP updates

CCNA CHAPTER 14 BY jetarvind kumar madhukar

Education

Transcript of CCNA CHAPTER 14 BY jetarvind kumar madhukar