Ccna3 M9 Vlan Trunking Protocol

CCNA – Semester3

Module 9 VLAN Trunking Protocol

Objectives

• Origins and functions of VLAN trunking • Define VTP • Inter-VLAN routing

Trunking

History of trunking

• In radio technologies, a trunk is a single communications line that carries multiple channels of radio signals.

Trunk in VLAN

• The same principle of trunking is applied to network switching technologies. • A trunk is a physical and logical connection between two switches across which network traffic travels.

Trunking protocols • Trunking protocols were developed to effectively manage the transfer of frames from different VLANs on a single physical line. • Two types of trunking mechanisms exist: – frame filtering – frame tagging.

Frame Filtering

Frames Tagging • Every frame is appended with a tag or VLAN ID. • Each switch examines every frame’s VLAN ID before forwarding. • Frame’s VLAN ID is removed before transmitted to end stations • Requires less administration • Scalable to large network

Trunking Protocol

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The most common tagging schemes for Ethernet segments are listed below: • ISL – Cisco proprietary Inter-Switch Link protocol. • 802.1Q – IEEE standard that will be focused on in this section.

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Trunk ports speed must be at least 100Mbps

VLANs and Trunking • Switch removes the identifier before the frame is transmitted to the target end station. • Frame tagging functions at Layer 2. • A trunk link does not belong to a specific VLAN.

VLANs and Trunking • ISL is a protocol that maintains VLAN information as traffic flows between the switches. With ISL, an Ethernet frame is encapsulated with a header that contains a VLAN ID.

Trunking configuration

Trunking modes

Show port capabilities • Determine what encapsulation the port can support (or show interfaces switchport).

Show trunk • Verify that trunking has been configured and verify the settings (or show interfaces trunk)

VTP

VTP Introduction

• With VTP, VLAN configuration is consistently maintained across a common administrative domain. • VTP is a messaging protocol that uses Layer 2 trunk frames to manage the addition, deletion, and renaming of VLANs on a single domain.

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

VTP header • The VTP header varies, depending upon the type of VTP message, but generally, four items are found in all VTP messages: – VTP protocol version: Either Version 1 or 2 – VTP message type: Indicates one of four types – Management domain name length: Indicates size of the name that follows – Management domain name: The name configured for the management domain

VTP modes • VTP switches operate in one of three modes: – Server – Client – Transparent

VTP revision number •

VLANs detected within the advertisements serve as notification to the switch that traffic with the newly defined VLAN IDs may be expected.

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VTP maintains its own NVRAM. An erase startup-configuration clears the NVRAM of configuration commands, but not the VTP database revision number. To set the configuration revision number back to zero, the switch must be rebooted.

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VTP advertisement • Each switch advertises on its trunk ports, its management domain, configuration revision number, the VLANs that it knows about, and certain parameters for each known VLAN. • These advertisement frames are sent to a multicast address so that all neighboring devices can receive the frames.

VTP advertisements • There are two types of VTP advertisements: • Requests from clients that want information at bootup • Response from servers

• There are three types of VTP messages: • Advertisement requests • Summary advertisements • Subset advertisements

VTP advertisements

VTP Implementation • By default, server and client Catalyst switches issue summary advertisements every 5 minutes. • Subset advertisements contain detailed information about VLANs such as VTP version type, domain name and related fields, and the configuration revision number. The following can trigger these advertisements: – – – –

Creating or deleting a VLAN Suspending or activating a VLAN Changing the name of a VLAN Changing the maximum transmission unit (MTU) of a VLAN

VTP Implementation • Advertisements may contain some or all of the following information: – Management domain name. Advertisements with different names are ignored. – Configuration revision number. – Message Digest 5 (MD5) password. – Updater identity.

VTP version • Two different versions of VTP are available, Version 1 and Version 2. • The two versions are not interoperable. • Configure the VTP version on a Cisco IOS command-based switch: Switch#vlan database Switch(vlan)#vtp v2-mode

Configure VTP domain Switch(vlan)#vtp domain domain_name Switch(vlan)#vtp password password Switch(vlan)#vtp {client | server | transparent} • The domain name can be between 1 and 32 characters. • The password must be between 8 and 64 characters long.

Add switch to VTP domain • • • •

Clear the configuration (erase startup) Clear the VTP file (delete flash:vlan.dat) Powercycle the switches Configure VTP mode and domain name (domain name can be learned automatically on client switches) • Password protect for the domain • Configure a trunk port that connect to a switch in the domain.

Show vtp status

Show vtp counters

Inter-VLAN Routing Overview

Between VLANs

Communicating between VLANs

Router on a Stick •

Two of the most common issues that arise in a multipleVLAN environment are: – The need for end user devices to reach non-local hosts – The need for hosts on different VLANs to communicate

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The router-on-a-stick designs employ a single trunk link that connects the router to the rest of the campus network.

ISL and 802.1q •

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As the number of VLANs increases on a network, the physical approach of having one router interface per VLAN quickly becomes unscalable. Networks with many VLANs must use VLAN trunking to assign multiple VLANs to a single router interface.

Inter-VLAN with trunking •

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The primary advantage of using a trunk link is a reduction in the number of router and switch ports used. Not only can this save money, it can also reduce configuration complexity. Consequently, the trunkconnected router approach can scale to a much larger number of VLANs than a one-link-per-VLAN design.

Subinterfaces and VLANs

Configure Inter-VLAN Routing • In order for inter-VLAN routing to work properly, all of the routers and switches involved must support the same encapsulation. • To define subinterfaces on a physical interface, perform the following tasks: – Identify the interface. – Define the VLAN encapsulation. – Assign an IP address to the interface.

Configure Inter-VLAN Routing Router(config)#interface fastethernet port-number. subinterfacenumber Router(config-if)#encapsulation dot1q vlan-number Router(config-if)#ip address ip-address subnet-mask

Inter-VLAN example

Summary • • • •

The origins and functions of VLAN trunking IEEE 802.1Q & Cisco ISL Definition of VLAN Trunking Protocol (VTP) The contents of VTP messages and the three VTP modes • Configuring and verifying VTP on an IOS-based switch • Configuring inter-VLAN routing using subinterfaces on a router port

Lab 1: VLAN & VTP • Configure VTP domain CCNA, password class, version 2. • VLANs: Associate, Professional, Specialist • Trunk ports: f0/24

Ports ->

Default

Associate

Professional

Specialist

Server

1 – 3, 6

4,5,8 – 12

7,13 – 19

20 – 23

Client

2–9

1, 10 – 15

15 – 18, 20

19, 21 – 23

Lab Topology • IP range: 172.20.0.0/16 • Vlan Default (port 1 – 5) needs 5 IPs • Vlan Sales (port 6 – 10) needs 100 IPs • Vlan Engineer (port 11 – 15) needs 50 IPs • Vlan Marketing (port 16 – 23) needs 100 IPs

CCNA3 – Module9