1 © 2003, Cisco Systems, Inc. All rights reserved. CCNA 3 v3.0 Module 9 VLAN Trunking Protocol Cisco Networking Academy.

1© 2003, Cisco Systems, Inc. All rights reserved.

CCNA 3 v3.0 Module 9VLAN Trunking Protocol

Cisco Networking Academy


Objectives

• Trunking

• VTP

• Inter-VLAN routing


Trunking Concepts

Trunking links between switches allow for the sharing of VLAN information.


Frame Filtering


Frame Tagging


VLANs and Trunking

“Multi-colored link”


Inter-Switch Link Protocol – Cisco


Frame Tagging and Encapsulation Methods

Cisco

IEEE


VLAN Trunking Protocol (VTP)

The role of VTP is to maintain VLAN configuration consistency across a common network administration domain.


VTP Mode Comparison

A transparent switch will not modify its database when updates are received, nor will the switch send out an update indicating a change in its VLAN status.

Except for forwarding VTP advertisements, VTP is disabled on a transparent switch.


VTP Operation


VTP Implementation

• There are two types of VTP advertisements:1. Requests from clients that want information at

bootup

2. Responses from servers

• There are three types of VTP messages:1. Advertisement requests

2. Summary advertisements

3. Subset advertisements


VTP and Trunk Links

• VTP messages are encapsulated in either ISL or IEEE 802.1Q protocol frames, and passed across trunk links to other devices.


VTP Basic Configuration Steps

1. Determine the version number

2. Choose the domain

3. Choose the VTP mode

• Server or Client or Transparent

• Default is Server

4. Password protect the domain


VTP Server vs. VTP Client

• VLANs can only be created or deleted on a VTP Server switch.

• VTP Client switches cannot create or delete VLANs.

– However, VTP Clients can update VTP Servers if they have a higher revision number

• Transparent Switches can add and delete VLANs but this information is not passed to the other switches in the VTP Domain.


Inter-VLAN Routing


Inter-VLAN Issues and Solutions

Two of the most common issues that arise in a multiple-VLAN environment are as follows:

1. The need for end-user devices to reach nonlocal hosts

2. The need for hosts on different VLANs to communicate


“Router-on-a-Stick”

I’m like a lollipop!


Physical and Logical Interfaces

IEEE 802.1q is more common


Dividing Physical Interfaces into Subinterfaces


Configuring Inter-VLAN Routing


Two Options for Inter-VLAN Routing

If "native" command is NOT supported:

interface Fastethernet0/0

description Dot1q Trunk to Switch-2950

ip address 10.1.1.1 255.255.255.0

speed 100

full-duplex

!

interface Fastethernet0/0.10

encapsulation dot1q 10

ip address 10.1.10.1 255.255.255.0

!



ip address 10.1.20.1 255.255.255.0

If "native" command IS supported:

interface Fastethernet0/0

description Dot1q Trunk to Switch-2950

no ip address

speed 100

full-duplex

!


encapsulation dot1q 1 native

ip address 10.1.1.1 255.255.255.0

!



ip address 10.1.10.1 255.255.255.0

!



ip address 10.1.20.1 255.255.255.0


The ‘native’ Command

• The ‘encapsulation dot1Q 1 native’ command was added in Cisco IOS version 12.1(3)T.

• If you are using an earlier version of Cisco IOS, refer to the 802.1Q configuration on the previous slide.

• The minimum IOS release required to support 802.1Q trunking on a 2620 or 2621 router is 12.0(1)T.

• The native VLAN is used for untagged traffic when the port is in 802.1Q trunking mode.

–While configuring 802.1Q trunking, it is very important to keep in mind that the native VLAN must be configured the same on each side of the trunk link.

1 © 2003, Cisco Systems, Inc. All rights reserved. CCNA 3 v3.0 Module 9 VLAN Trunking Protocol Cisco Networking Academy.

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