CCNP Switch Certification Guide: Aggregating Switch Links

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

• Switch Port Aggregation with EtherChannel—This section discusses the concept of aggregating, or "bundling," physical ports into a single logical link. Methods for load balancing traffic across the physical links also are covered.
• EtherChannel Negotiation Protocols—This section discusses two protocols that dynamically negotiate and control EtherChannels: Port Aggregation Protocol (PAgP), a Cisco proprietary protocol, and Link Aggregation Control Protocol (LACP), a standards-based protocol.
• EtherChannel Configuration—This section discusses the Catalyst switch commands needed to configure EtherChannel.
• Troubleshooting an EtherChannel—This section gives a brief summary of things to consider and commands to use when an aggregated link is not operating properly.

In previous chapters, you learned about connecting switches and organizing users and devices into common workgroups. Using these principles, end users can be given effective access to resources both on and off the campus network. However, today's mission-critical applications and services demand networks that provide high availability and reliability.

This chapter presents technologies that you can use in a campus network to provide higher bandwidth and reliability between switches.

"Do I Know This Already?" Quiz

The "Do I Know This Already?" quiz allows you to assess whether you should read this entire chapter thoroughly or jump to the "Exam Preparation Tasks" section. If you are in doubt based on your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 6-1 outlines the major headings in this chapter and the "Do I Know This Already?" quiz questions that go with them. You can find the answers in Appendix A, "Answers to the 'Do I Know This Already?' Quizzes."

Table 6-1. "Do I Know This Already?" Foundation Topics Section-to-Question Mapping

1. If Fast Ethernet ports are bundled into an EtherChannel, what is the maximum throughput supported on a Catalyst switch?

   1. 100 Mbps
   2. 200 Mbps
   3. 400 Mbps
   4. 800 Mbps
   5. 1600 Mbps

2. Which of these methods distributes traffic over an EtherChannel?

   1. Round robin
   2. Least-used link
   3. A function of address
   4. A function of packet size

3. What type of interface represents an EtherChannel as a whole?

   1. Channel
   2. Port
   3. Port channel
   4. Channel port

4. Which of the following is not a valid method for EtherChannel load balancing?

   1. Source MAC address
   2. Source and destination MAC addresses
   3. Source IP address
   4. IP precedence
   5. UDP/TCP port

5. How can the EtherChannel load-balancing method be set?

   1. Per switch port
   2. Per EtherChannel
   3. Globally per switch
   4. Can't be configured

6. What logical operation is performed to calculate EtherChannel load balancing as a function of two addresses?

   1. OR
   2. AND
   3. XOR
   4. NOR

7. Which one of the following is a valid combination of ports for an EtherChannel?

   1. Two access links (one VLAN 5, one VLAN 5)
   2. Two access links (one VLAN 1, one VLAN 10)
   3. Two trunk links (one VLANs 1 to 10, one VLANs 1, 11 to 20)
   4. Two Fast Ethernet links (both full duplex, one 10 Mbps)

8. Which of these is a method for negotiating an EtherChannel?

   1. PAP
   2. CHAP
   3. LAPD
   4. LACP

9. Which of the following is a valid EtherChannel negotiation mode combination between two switches?

   1. PAgP auto, PAgP auto
   2. PAgP auto, PAgP desirable
   3. on, PAgP auto
   4. LACP passive, LACP passive

10. When is PAgP's "desirable silent" mode useful?

    1. When the switch should not send PAgP frames
    2. When the switch should not form an EtherChannel
    3. When the switch should not expect to receive PAgP frames
    4. When the switch is using LACP mode

11. Which of the following EtherChannel modes does not send or receive any negotiation frames?

    1. channel-group 1 mode passive
    2. channel-group 1 mode active
    3. channel-group 1 mode on
    4. channel-group 1 mode desirable
    5. channel-group 1 mode auto

12. Two computers are the only hosts sending IP data across an EtherChannel between two switches. Several different applications are being used between them. Which of these load-balancing methods would be more likely to use the most links in the EtherChannel?

    1. Source and destination MAC addresses.
    2. Source and destination IP addresses.
    3. Source and destination TCP/UDP ports.
    4. None of the other answers is correct.

13. Which command can be used to see the status of an EtherChannel's links?

    1. show channel link
    2. show etherchannel status
    3. show etherchannel summary
    4. show ether channel status