Networking Chapter 13 Ccna Guide Cisco Networking Fundamentals Fourth Edition Advanced Switching Concepts Glance

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13-1

Chapter 13

Advanced Switching Concepts

At a Glance

Instructor’s Manual Table of Contents

• Overview

• Objectives

• Teaching Tips

• Quick Quizzes

• Class Discussion Topics

• Additional Projects

• Additional Resources

• Key Terms

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13-2

Lecture Notes

Overview

This chapter builds on the topics introduced in Chapter 12, in which your students learned

about switching concepts and basic switch configuration. In Chapter 13, they expand on

Chapter Objectives

• Explain how the Spanning Tree Protocol works and describe its benefits

• Describe the benefits of virtual LANs

• Configure a VLAN

• Understand the Purpose of the VLAN trunking protocol (VTP)

• Configure VTP

Teaching Tips

Spanning Tree Protocol

1. Define physical path loops as a physical connection created when network devices are

2. Mention that the drawback to this configuration is that it can result in endless packet

looping.

4. Explain that STP uses the Spanning Tree Algorithm (STA) to interrupt the logical loop

5. Explain that switches and bridges on a network use an election process to configure a

6. Mention that bridges use STP to transfer the information about each bridge’s MAC

address and priority number.

7. Define bridge protocol data units (BPDU) or configuration bridge protocol data units

8. Explain that each bridge or switch determines which of its own ports offers the best

path to the root bridge. The BPDU messages are sent between the root bridge and the

9. Mention that once the root bridge is determined and the switches and bridges have

11. Define stable states as the normal operating states of ports when the root bridge is

available and all paths are functioning as expected. The stable states are as follows:

12. Explain that transitory states prevent logical loops during a period of transition from

14. Ports on STP-enabled devices move through the different states as indicated in the

following list:

15. Explain that when the topology is changed, STP-enabled devices react automatically. If

16. Explain that Per-VLAN STP (PVSTP) operates on VLANs and treats all VLANs

Teaching

Tip

PVSTP provides the ability to load balance traffic between the VLANs. VSTP

uses Cisco’s proprietary ISL trunking protocol. It allows a VLAN trunk to block

for some VLANs and forward for others. The technology is advanced enough to

prevent bridge loops on the VLANs.

17. Explain that Spanning Tree PortFast allows you to configure a switch to bypass some of

19. Explain that Rapid STP (RSTP) 802.1w takes the basis of 802.1d (STP) and

Virtual LANs

1. Define a Virtual LAN (VLAN) as a grouping of network devices that is not restricted to

2. Define a broadcast domain as a group of network devices that will receive LAN

4. Explain that you can create multiple VLANs on a single switch or even create one

VLAN across multiple switches. Use Figures 13-2 and 13-3 to illustrate your

explanation.

Teaching

Tip

Although VLANs can separate broadcast domains, as can routers, this does not

mean that they segment at layer 3. A VLAN is a layer 2 implementation, and

does not affect layer 3 logical addressing.

Benefits of VLANs

1. Describe some of the benefits offered by a VLAN, including the following:

a. Ease of adding and moving stations on the LAN

2. Explain that VLANs help to reduce the cost of moving employees from one location to

3. Because the administrator can set the size of the broadcast domain, the VLAN gives the

4. Explain that dividing the broadcast domains into logical groups increases security

5. Mention that VLANs can be configured by network administrators to allow

membership only for certain devices.

Teaching

Tip

The restrictions that can be used are similar to those of a firewall; unwanted

users can be flagged or disabled, and administrative alerts can be sent if someone

attempts to infiltrate a given VLAN. This type of security is typically

implemented by grouping switch ports together according to the type of

applications and access privileges required.

Dynamic vs. Static VLANs

1. Explain that static VLANs are configured port-by-port, with each port being associated

2. Explain that dynamic VLAN ports can automatically determine their VLAN

3. Mention that a dynamic VLAN could prove to be more time-consuming than the static

VLAN.

5. Mention that on a dynamic VLAN, moving a cable from one switch port to another is

Quick Quiz 1

1. A(n) ____ is a physical connection created when network devices are connected to one

another by two or more physical media links.

2. STP uses the ____ to interrupt the logical loop created by a physical loop in a

bridged/switched environment.

3. A(n) ____ is a grouping of network devices that is not restricted to a physical segment

or switch.

4. A(n) ____ is a group of network devices that will receive LAN broadcast traffic from

each other.

VLAN Standardization

1. Mention that before VLAN was an IEEE standard, early implementations depended on

3. Mention that the IEEE 802.1q specification that defines VLANs recommends frame

4. Explain that frame tagging involves adding a four-byte field to the actual Ethernet

frame to identify the VLAN and other pertinent information. It makes it easier and more

5. Mention that the two most common types of frame tagging (encapsulation) are 802.1q

Teaching

Tip

The additional header with the VLAN addressing information is stripped off the

frame before it reaches the connected host stations. Otherwise, non-VLAN-aware

host stations would see the additional information as a long frame or jabber.

Creating VLANs

1. Explain that you can create VLANs by entering the (config–vlan)# mode and

2. To use the config-vlan mode, you type the following:

3. Mention that to use the VLAN configuration mode, you start by entering the VLAN

5. To remove a VLAN, use the no parameter: Rm410HL(config)#no vlan 2.

Teaching

Tip

You can use the show vlan [#] command to gather information about a

specific VLAN (instead of listing all VLANs). The show vlan–

membership command gives a variation of the same output as the show

vlan command.

Link Types and Configuration

1. Mention that two types of links are on Cisco switches: trunk links and access links.

2. Define trunk links as switch–to– switch or switch-to-router links that can carry traffic

3. Mention that you choose from five different states for a trunk link:

a. Auto

5. Mention that you can configure a name for each port on a switch. This is useful when

VLAN Trunking Protocol

1. Define VLAN trunking protocol (VTP) as a layer 2 messaging protocol that manages all

2. Explain that VTP devices are organized into domains. Each switch can only be in one

VTP domain at a time, and all devices that need to share information must be in the

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13-8

Teaching

Tip

If all of your switches are in the same VLAN, configuring a VTP domain is not

necessary.

3. Describe the following VTP device modes:

4. Explain that VTP pruning option reduces the number of VTP updates that traverse a

link. It is off by default on all switches.

6. Mention that VLAN 1 is not eligible to be pruned because it is an administrative (and

default) VLAN.

Nonswitching Hubs and VLANs

1. Describe the following important considerations:

a. If you insert a hub into a port on the switch and then connect several devices to

the hub, all the systems attached to that hub will be in the same VLAN.

b. If you must move a single workstation that is attached to a hub with several

workstations, you will have to physically attach the device to another hub or

Routers and VLANs

1. Explain that routers can be used with VLANs to increase security, and must be used to

manage traffic between different VLANs.

2. Mention that routers can implement access lists, which increase inter-VLAN security. A

router allows restrictions to be placed on station addresses, application types, and

protocol types. Use Figure 13-5 to illustrate your explanation.

Teaching

Tip

Sometimes it is necessary to communicate with devices outside the VLAN.

Because each VLAN is considered a different logical network, a router is

required to move traffic between the two VLANs.

3. Explain that the router can either be an onboard Route Switch Module (RSM) or an

5. Trunking is the process of using either ISL or 802.1q to allow multiple VLAN traffic on

the same link. For instance, an ISL trunk link would encapsulate each packet with the

Quick Quiz 2

1. ____ was a complex process that involved one table for each VLAN and a master table

that was shared by all VLANs.

2. When creating its VLAN standard, the IEEE did not choose the frame-filtering method.

Instead, the IEEE 802.1q specification that defines VLANs recommends ____ (also

known as frame identification).

3. ____ links are switch-to-switch or switch-to-router links that can carry traffic from

multiple VLANs.

4. Cisco created the ____ to manage all of the configured VLANs that traverse trunks

between switches.

Class Discussion Topics

1. What are the advantages and drawbacks of physical path loops?

2. What are VTP domains?

Additional Projects

1. VLAN trunking protocol (VTP) is a Data Link layer protocol used to track VLAN

membership changes across trunk links between VTP-enabled devices.

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13-10

Ask your students to read more about VTP and write a report explaining its most

important features. Use the following link as a starting point:

2. Ask your students to read the following article about Spanning Tree PortFast BPDU

Guard Enhancement at

Additional Resources

1. 802.1Q – Virtual LANs

2. LAN emulation

3. Cisco Inter-Switch Link

4. Route Switch Module

5. Virtual LAN

Key Terms

➢ access list A list of criteria to which all packets are compared.

➢ blocking A port state on a switch that indicates the port is receiving and sending

➢ forwarding The state of a port on a switch or bridge that indicates it will learn MAC

addresses and forward frames out that port.

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13-11

➢ frame filtering A technique used on early VLAN implementations that employed the

use of multiple switching tables.

Rapid Spanning Tree Protocol.

➢ Inter-Switch Link (ISL) protocol A frame-tagging method for VLANs proprietary to

Cisco devices; uses a 26-byte header.

➢ LAN emulation (LANE) A frame-tagging method used for VLANs on Asynchronous

Transfer Mode (ATM) devices.

VLAN 1.

➢ Per-VLAN Spanning Tree Protocol (PVSTP) A protocol that operates on VLANs

and treats all connected VLANs as separate physical networks.

➢ physical path loops A loop that occurs when network devices are connected to one

another by two or more physical media links.

➢ router-on-a-stick The process of utilizing one physical router interface (with

subinterfaces configured) to route traffic for multiple VLANs.

➢ Spanning Tree Algorithm (STA) The algorithm used by STP to ensure that logical

loops are not created in the presence of physical loops on a network.

➢ Spanning Tree Protocol (STP) The Data Link layer protocol used by switches and

➢ VTP client A VTP device that receives and shares VTP information, but does not add,

modify, or delete information and does not store the VTP database in NVRAM.

➢ VTP domain A group of VTP-enabled devices configured under one name to share

VLAN information.

➢ VTP pruning An option configured for an entire VTP domain that prohibits the