BCMSN Exam Certification Guide

346 Chapter 14: Router Redundancy and Load Balancing

By default, any client from any IP address can make connections to the virtual server. To limit the access, define only the IP subnet or address range (with subnet mask) that is allowed access. The inverse-mask here resembles that of an access list, where a 1-bit ignores and a 0-bit matches.

Step 5 Put the virtual server into service:

Switch(config-slb-vserver)# inservice

By default, SLB does not allow connections to be made to a virtual server until it is put into service. If a virtual server needs to be temporarily disabled for some reason, use the no inservice command.

Verifying Redundancy and Load Balancing

To verify the operation of the features discussed in this chapter, you can use the commands listed in Table 14-3. In particular, look for the active router, standby or backup routers, and load-balancing methods in use.

Table 14-3 Redundancy and Load Balancing Verification Commands

Foundation Summary 347

Foundation Summary

The Foundation Summary is a collection of information that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary can help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, this information is a convenient way to review the day before the exam.

Table 14-4 A Comparison of Router Redundancy Protocols

Table 14-5 HSRP Configuration Commands

348 Chapter 14: Router Redundancy and Load Balancing

Table 14-6 VRRP Configuration Commands

Table 14-7 GLBP Configuration Commands

350 Chapter 14: Router Redundancy and Load Balancing

Q&A

The questions and scenarios in this book are more difficult than what you should experience on the actual exam. The questions do not attempt to cover more breadth or depth than the exam; however, they are designed to make sure that you know the answer. Rather than allowing you to derive the answers from clues hidden inside the questions themselves, the questions challenge your understanding and recall of the subject. Hopefully, these questions will help limit the number of exam questions on which you narrow your choices to two options and then guess.

You can find the answers to these questions in Appendix A.

1.A multilayer switch has been configured with the command standby 5 priority 120. What router redundancy protocol is being used?

2.What feature can you use to prevent other routers from accidentally participating in an HSRP group?

3.What command can configure an HSRP group to use a virtual router address of 192.168.222.100?

4.The show standby vlan 271 command produces the following output:

Vlan271 - Group 1

Local state is Active, priority 210, may preempt

Hellotime 3 holdtime 40 configured hellotime 3 sec holdtime 40 sec Next hello sent in 00:00:00.594

Virtual IP address is 192.168.111.1 configured Secondary virtual IP address 10.1.111.1 Secondary virtual IP address 172.21.111.1

Active router is local

Standby router is unknown expires in 00:00:37 Standby virtual mac address is 0000.0c07.ac01 2 state changes, last state change 5d17h

If the local router fails, which router takes over the active role for the virtual router address 192.168.111.1?

5.What is meant by preempting in HSRP?

6.What protocols discussed in this chapter support interface tracking?

Q&A 351

7.The show standby brief command has been used to check the status of all HSRP groups on the local router. The output from this command is as follows:

Switch# show standby brief

P indicates configured to preempt.

Each interface is shown to have Group 1. Is this a problem?

8.How many HSRP groups are needed to load balance traffic over two routers?

9.What load-balancing methods can GLBP use?

10.What command can you use to see the status of the active and standby routers on the VLAN 171 interface?

11.How many GLBP groups are needed to load balance traffic over four routers?

12.When should you use SLB?

13.What command defines and names an SLB server farm?

14.A virtual server has just been defined with the following commands:

ip slb vserver CISCO serverfarm CISCO-FARM virtual 192.168.199.17

Can the virtual server be used immediately? If not, what additional command is needed?

This chapter covers the following topics that you need to master for the CCNP BCMSN exam:

■Multicast Overview—This section discusses multicast addressing and general multicast traffic forwarding.

■Routing Multicast Traffic—This section covers the protocols used by Layer 3 devices to maintain multicast groups and their members, and to constrain multicast forwarding.

■Switching Multicast Traffic—This section explains techniques that you can use to intelligently forward multicast traffic at Layer 2.

■Verifying Multicast—This section provides a brief summary of the commands that can verify the configuration and operation of multicast routing and switching.

C H A P T E R 15

Multicast

Multicast traffic is typically sent by one source and received by a group of recipients, spread throughout a network and changing over time. Examples of multicast traffic include video streams for instruction or entertainment, certain audio conference calls, and one-to-many PC file imaging applications.

Because not everyone on a network wants to receive the traffic from a multicast source, switches and routers must have some means to forward traffic to exactly the destinations that want to receive it. This chapter covers IP multicast and the various protocols used to forward multicast packets.

“Do I Know This Already?” Quiz

The purpose of the “Do I Know This Already?” quiz is to help you decide what parts of this chapter to use. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now.

The quiz, derived from the major sections in the “Foundation Topics” portion of the chapter, helps you determine how to spend your limited study time.

Table 15-1 outlines the major topics discussed in this chapter and the “Do I Know This Already?” quiz questions that correspond to those topics.

Table 15-1 “Do I Know This Already?” Foundation Topics Section-to-Question Mapping

354 Chapter 15: Multicast

CAUTION The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark this question wrong. Giving yourself credit for an answer you correctly guess skews your selfassessment results and might give you a false sense of security.

1.How many sources are typically present in a multicast group?

a.1

b.2

c.As many as are registered with the router

d.Cannot be determined

2.Which one of the following is a multicast address?

a.128.224.1.1

b.172.17.224.1

c.225.17.1.1

d.242.17.1.1

3.224.1.2.3 corresponds to which of the following MAC addresses?

a.0102.0300.0000

b.0100.5e01.0203

c.e000.0001.0203

d.1000.5e01.0203

4.How many unique multicast IP addresses can correspond to one multicast MAC address?

a.1

b.2

c.8

d.32

“Do I Know This Already?” Quiz 355

5.Which of the following is the test that is performed before a multicast packet can be forwarded?

a.Shortest Path First

b.Cyclic Redundancy Check

c.Reverse Path Forwarding

d.Multicast Route Verification

6.Which protocol registers hosts for multicast group membership?

a.CGMP

b.IGRP

c.IGMP

d.PIM

7.A host sends Internet Group Management Protocol (IGMP) packets to which of the following?

a.The local switch

b.The local router

c.The multicast source

d.The root of the multicast tree

8.If a multicast group has recipients on every subnet, which of the PIM modes should be used?

a.Dense mode

b.Sparse mode

c.Sparse-compress mode

d.Flood mode

9.Which type of tree structure is built for sparse mode multicast routing?

a.Spanning Tree

b.Shared Tree

c.Sparse Tree

d.Simple Tree