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CCNA Voice 640-461: Understanding the Cisco IP Phone Concepts and Registration

Chapter Description

This chapter walks you through the key concepts and technologies used to build a Cisco VoIP network while working towards your CCNA Voice certification.

This chapter includes the following topics:

  • Connecting and Powering Cisco IP Phones: To provide a centralized power system, the Cisco IP Phones must receive their power from a centralized source using PoE. This section discusses the different options for PoE and the selection criterion of each.
  • VLAN Concepts and Configuration: VLANs allow you to break the switched network into logical pieces to provide management and security boundaries between the voice and data network. This section discusses the concepts and configuration behind VLAN.
  • Understanding Cisco IP Phone Boot Process: This section discusses the foundations of the Cisco IP Phone boot process. Understanding this process is critical to troubleshooting issues with the IP Telephony system.
  • Configuring a Router-Based DHCP Server: This section discusses configuring a Cisco router as a DHCP server for your network.
  • Setting the Clock of a Cisco Device with NTP: Because a VoIP network heavily depends on accurate time, the sole focus of this section is keeping the clocks accurate on Cisco devices by using NTP.
  • IP Phone Registration: Once the Cisco IP Phone receives all its network configuration settings, it is ready to speak to a call processing agent. This section describes the process and protocols that make it happen.

You walk into the new corporate headquarters for Fizzmo Corp. On the top of each desk is a Cisco 7945G IP Phone, glowing with a full-color display and two line instances. Smiling, courteous agents are busy taking phone calls from callers excited to purchase the latest Fizzmo wares. Samantha (located in the north corner) is checking her visual voicemail, while Emilio (located in the south hall) is getting the latest weather report through an XML IP phone service.

How did we get here? How do you take a newly constructed building and transform it into a bustling call center? That's what this chapter is all about. We walk through the key concepts and technologies used to build a Cisco VoIP network. By the time you are done with this chapter, you will have all the conceptual knowledge you need to have in place before you can move into the installation and configuration of the Cisco VoIP system.

"Do I Know This Already?" Quiz

The "Do I Know This Already?" quiz allows you to assess whether you should read this entire chapter or simply jump to the "Exam Preparation Tasks" section for review. If you are in doubt, read the entire chapter. Table 3-1 outlines the major headings in this chapter and the corresponding "Do I Know This Already?" quiz questions. You can find the answers in Appendix A, "Answers Appendix."

Table 3-1. "Do I Know This Already?" Foundation Topics Section-to-Question Mapping

Foundation Topics Section

Questions Covered in This Section

Connecting and Powering Cisco IP Phones


VLAN Concepts and Configuration


Understanding Cisco IP Phone Boot Process


Configuring a Router-Based DHCP Server


Setting the Clock of a Cisco Device with NTP


IP Phone Registration


  1. Which of the following is an industry standard used for powering devices using an Ethernet cable?

    1. Cisco Inline Power
    2. 802.1Q
    3. 802.3af
    4. Local power brick
  2. Which of the following are valid methods for powering a Cisco IP Phone? (Select all that apply.)

    1. Power brick
    2. Crossover coupler
    3. PoE
    4. Using pins 1, 2, 3, and 4
  3. Which of the following terms are synonymous with a VLAN? (Choose two.)

    1. IP subnet
    2. Port security
    3. Broadcast domain
    4. Collision domain
  4. Which of the following trunking protocols would be used to connect a Cisco switch to a non-Cisco switch device?

    1. VTP
    2. 802.3af
    3. 802.1Q
    4. ISL
  5. How should you configure a port supporting voice and data VLANs that is connected to a Cisco IP Phone?

    1. Access
    2. Trunk
    3. Dynamic
    4. Dynamic Desired
  6. How does a device attached to a Cisco IP Phone send data to the switch?

    1. As tagged (using the voice VLAN)
    2. As untagged
    3. As tagged (using the data VLAN)
    4. As tagged (using the CoS value)
  7. Which of the following commands should you use to configure a port for a voice VLAN 12?

    1. switchport mode voice vlan 12
    2. switchport trunk voice vlan 12
    3. switchport voice vlan 12
    4. switchport vlan 12 voice
  8. Which of the following commands would you use to forward DHCP requests from an interface connected to the subnet to a DHCP server with the IP address

    1. forward-protocol
    2. forward-protocol dhcp
    3. ip helper-address
    4. ip helper-address
  9. How does the Cisco switch communicate voice VLAN information after a Cisco IP Phone has received PoE and started the boot process?

    1. Through CDP
    2. Using 802.1Q
    3. Using the proprietary ISL protocol
    4. Voice VLAN information must be statically entered on the Cisco IP Phone.
  10. Which DHCP option provides the IP address of a TFTP server to a Cisco IP Phone?

    1. Option 10
    2. Option 15
    3. Option 150
    4. Option 290
  11. Which of the following NTP stratum numbers would be considered the best?

    1. Stratum 0
    2. Stratum 1
    3. Stratum 2
    4. Stratum 3
  12. Which of the following protocols could be used for Cisco IP Phone registration? (Choose two.)

    1. SCCP
    2. SIP
    3. DHCP
    4. H.323
2. Foundation Topics: Connecting and Powering Cisco IP Phones | Next Section