Server Load Balancing (SLB) 345 Step 2 Choose a load-balancing method. Switch(config-slb-sfarm)# predictor {roundrobin | leastconns} Either weighted round-robin (the default) or weighted least connections can be used. Step 3 Identify the real servers in the server farm: Switch(config-slb-sfarm)# real ip-address The server’s actual IP address is given. Step 4 Assign a weight for the relative server capacity: Switch(config-slb-real)# weight weighting-value The weighting value (1 to 255, default 8) indicates the server’s capacity to accept new connections, relative to the other real servers in the server farm. Step 5 Put the real server into service: Switch(config-slb-real)# inservice By default, SLB cannot use a real server until it is manually put into service. Later, the real server can be taken out of service for maintenance with the no inservice command. This removes it from use in the SLB server farm until it is returned to service again. (To take a real server out of service, first get into the real server configuration mode by using the commands from Steps 1 and 3.) Virtual Servers Configure each virtual server by the following series of steps: Step 1 Name the virtual server: Switch(config)# ip slb vserver virtual-server-name The virtual server is given a descriptive name, up to 15 characters. Step 2 Assign the virtual server to a server farm: Switch(config-slb-vserver)# serverfarm serverfarm-name SLB uses the virtual server as the front end for the server farm named. This server farm must already be configured, populated with one or more real servers. Step 3 Assign an IP address to the virtual server: Switch(config-slb-vserver)# virtual ip-address Step 4 Control access to the virtual server: Switch(config-slb-vserver)# client ip-address inverse-mask 1-58720-077-5.book Page 345 Tuesday, August 19, 2003 3:16 PM 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 Task Command Syntax HSRP and VRRP Show HSRP status. show standby brief Show HSRP on an interface. show standby type mod/num Show VRRP status. show vrrp brief all Show VRRP on an interface. show vrrp interface type mod/num GLBP Show status of a GLBP group. show glbp group SLB Show server farms. show ip slb serverfarms Show real servers. show ip slb reals Show virtual servers. show ip slb vserver Show current SLB connections. show ip slb conns 1-58720-077-5.book Page 346 Tuesday, August 19, 2003 3:16 PM 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 HSRP VRRP GLBP Standard? no; Cisco-proprietary, RFC 2281 yes; RFC 2338 no; Cisco-proprietary Router roles Active router, standby router Master router, backup router AVG, AVF Load balancing Only through multiple HSRP groups, different client gateways Only through multiple VRRP groups, different client gateways Inherent with one GLBP group; all clients use same gateway; several methods available Interface tracking yes no yes Virtual router MAC address 0000.0c07.acxx 0000.5e00.01xx assigned by AVG Table 14-5 HSRP Configuration Commands Task Command Syntax Set the HSRP priority. standby group priority priority Set the HSRP timers. standby group timers hello holdtime Allow router preemption. standby group preempt [delay seconds] Use group authentication. standby group authentication string Adjust priority by tracking an interface. standby group track type mod/num decrementvalue Assign the virtual router address. standby group ip ip-address [secondary] 1-58720-077-5.book Page 347 Tuesday, August 19, 2003 3:16 PM 348 Chapter 14: Router Redundancy and Load Balancing Table 14-6 VRRP Configuration Commands Task Command Syntax Assign a VRRP router priority (default 100). vrrp group priority level Alter the advertisement timer (default 1 second). vrrp group timers advertise [msec] interval Learn the advertisement interval from the master router. vrrp group timers learn Disable preempting (default is to preempt). no vrrp group preempt Change the preempt delay (default 0 seconds). vrrp group preempt [delay seconds] Use authentication for advertisements. vrrp group authentication string Assign a virtual IP address. vrrp group ip ip-address [secondary] Table 14-7 GLBP Configuration Commands Task Command Syntax Assign a GLBP priority. glbp group priority level Allow GLBP preemption. glbp group preempt [delay minimum seconds] Define an object to be tracked. track object-number interface type mod/num {line-protocol | ip routing} Define the weighting thresholds. glbp group weighting maximum [lower lower] [upper upper] Track an object. glbp group weighting track object-number [decrement value] Choose the load-balancing method. glbp group load-balancing [round-robin | weighted | host-dependent] Assign a virtual router address. glbp group ip [ip-address [secondary]] 1-58720-077-5.book Page 348 Tuesday, August 19, 2003 3:16 PM Foundation Summary 349 Table 14-8 SLB Configuration Commands Task Command Syntax Name a server farm. ip slb serverfarm serverfarm-name Choose a load-balancing method. predictor {roundrobin | leastconns} Identify a real server. real ip-address Assign a relative weight to the real server. weight weighting-value Enable the server for use. inservice Name the virtual server. ip slb vserver virtual-server-name Link the virtual server to a server farm. serverfarm serverfarm-name Limit access to the virtual server. client ip-address network-mask Define the virtual server IP address. virtual ip-address Enable the virtual server for use. inservice 1-58720-077-5.book Page 349 Tuesday, August 19, 2003 3:16 PM 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 under- standing 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? 1-58720-077-5.book Page 350 Tuesday, August 19, 2003 3:16 PM 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# ss ss hh hh oo oo ww ww ss ss tt tt aa aa nn nn dd dd bb bb yy yy bb bb rr rr ii ii ee ee ff ff P indicates configured to preempt. | Interface Grp Prio P State Active addr Standby addr Group addr Vl100 1 210 P Active local 192.168.75.2 192.168.75.1 Vl101 1 210 P Active local 192.168.107.2 192.168.107.1 Vl102 1 210 P Active local 192.168.71.2 192.168.71.1 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: ii ii pp pp ss ss ll ll bb bb vv vv ss ss ee ee rr rr vv vv ee ee rr rr CC CC II II SS SS CC CC OO OO ss ss ee ee rr rr vv vv ee ee rr rr ff ff aa aa rr rr mm mm CC CC II II SS SS CC CC OO OO FF FF AA AA RR RR MM MM vv vv ii ii rr rr tt tt uu uu aa aa ll ll 11 11 99 99 22 22 11 11 66 66 88 88 11 11 99 99 99 99 11 11 77 77 Can the virtual server be used immediately? If not, what additional command is needed? 1-58720-077-5.book Page 351 Tuesday, August 19, 2003 3:16 PM This chapter covers the following topics that you need to master for the CCNP BCMSN exam: ■ Multicast Overview—This section dis- cusses 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 intel- ligently 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 mul- ticast routing and switching. 1-58720-077-5.book Page 352 Tuesday, August 19, 2003 3:16 PM 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 Foundation Topics Section Questions Covered in This Section Multicast Overview 1–7 Routing Multicast Traffic 8–11 Switching Multicast Traffic 12 1-58720-077-5.book Page 353 Tuesday, August 19, 2003 3:16 PM 354 Chapter 15: Multicast 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 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 self- assessment results and might give you a false sense of security. 1-58720-077-5.book Page 354 Tuesday, August 19, 2003 3:16 PM [...]... switches The switches then learn of group members and their port locations 1-5 872 0- 077 -5.book Page 373 Tuesday, August 19, 2003 3:16 PM Q&A 373 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 answers Rather... 3:16 PM PART IV: Campus Network Services Chapter 16 Quality of Service Overview Chapter 17 Diffserv QoS Configuration Chapter 18 IP Telephony Chapter 19 Securing Switch Access Chapter 20 Securing with VLANs 1-5 872 0- 077 -5.book Page 375 Tuesday, August 19, 2003 3:16 PM This part of the book covers the following BCMSN exam topics: I Describe the quality issues with voice traffic on a switched data network,... when implementing IP telephony in a switched network environment I Plan QoS implementation within a multilayer switched network 1-5 872 0- 077 -5.book Page 376 Tuesday, August 19, 2003 3:16 PM This chapter covers the following topics that you need to master for the CCNP BCMSN exam: I DiffServ QoS—This section discusses the Differentiated Services QoS model, where QoS is defined as a per-hop behavior Each... PIM v2 BSRs show ip pim bsr-router Multicast Switching Table 15-3 lists those commands that you need to verify that IGMP snooping is configured and working as intended 1-5 872 0- 077 -5.book Page 370 Tuesday, August 19, 2003 3:16 PM 370 Chapter 15: Multicast Table 15-3 Commands for Verifying IGMP Operation Task Command Syntax List active IGMP groups and members show ip igmp groups Show IGMP activity on... to constrain the multicast flooding Although a router isn’t present, the switch can still listen to the membership reports being sent to the nonexistent router 1-5 872 0- 077 -5.book Page 371 Tuesday, August 19, 2003 3:16 PM Foundation Summary 371 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... recipients are leaf nodes Group extended from recipients toward RP; pruning only when member leaves group Sparse-Dense Mode (S,G) or (*,G) Hybrid on a per-group basis n/a 1-5 872 0- 077 -5.book Page 372 Tuesday, August 19, 2003 3:16 PM 372 Chapter 15: Multicast Table 15-5 IP PIM Multicast Configuration Commands Task Command Syntax Enable multicast routing ip multicast-routing Use PIM Dense Mode on an interface... to the “Foundation Summary” section and then go to the “Q&A” section at the end of the chapter Otherwise, move to Chapter 16, “Quality of Service Overview.” 1-5 872 0- 077 -5.book Page 3 57 Tuesday, August 19, 2003 3:16 PM Multicast Overview 3 57 Foundation Topics Multicast Overview In a network, three basic types of IP traffic traverse the routers and switches: I Unicast—Packets that are sent from one source... Layer 2 switch need when it is configured for CGMP? 17 When should IGMP snooping and CGMP be used together on a switch? 18 At a trade show, several PCs and servers are connected to a single Layer 2 switch The switch has CGMP enabled When a server begins to send video data to a multicast address, what happens to that traffic? 1-5 872 0- 077 -5.book Page 374 Tuesday, August 19, 2003 3:16 PM PART IV: Campus... multicast IP addresses Therefore, the host must receive and examine every frame that has the MAC address it is interested in—regardless to which of the 32 IP addresses the frame was originally destined The host must examine the IP header inside each frame to verify that the more specific IP multicast address is a desired multicast group 1-5 872 0- 077 -5.book Page 359 Tuesday, August 19, 2003 3:16 PM Routing... selection for a group is based on a hashing function The length of the hash mask controls the number of consecutive multicast groups that hash to the same RP 1-5 872 0- 077 -5.book Page 3 67 Tuesday, August 19, 2003 3:16 PM Switching Multicast Traffic 3 67 Next, you must identify each of the candidate RP routers Configure each RP with the following global configuration command: Switch(config)# ip pim rp-candidate . 11 11 66 66 88 88 11 11 99 99 99 99 11 11 77 77 Can the virtual server be used immediately? If not, what additional command is needed? 1-5 872 0- 077 -5.book Page 351 Tuesday, August 19, 2003 3:16. addr Vl100 1 210 P Active local 192.168 .75 .2 192.168 .75 .1 Vl101 1 210 P Active local 192.168.1 07. 2 192.168.1 07. 1 Vl102 1 210 P Active local 192.168 .71 .2 192.168 .71 .1 Each interface is shown to have. decrementvalue Assign the virtual router address. standby group ip ip-address [secondary] 1-5 872 0- 077 -5.book Page 3 47 Tuesday, August 19, 2003 3:16 PM 348 Chapter 14: Router Redundancy and Load