Excerpt from CCNA ICND2 Official Exam Certification Guide (CCNA Exams 640-816 and 640-802), 2nd Edition.
By Wendell Odom Published by Cisco Press ISBN-10: 1-58720-181-X ISBN-13: 978-1-58720-181-3

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This chapter covers the following subjects:

Global Unicast Addressing, Routing, and Subnetting: This section introduces the concepts behind unicast IPv6 addresses, IPv6 routing, and subnetting using IPv6, all in comparison to IPv4.

IPv6 Protocols and Addressing: This section examines the most common protocols used in conjunction with IPv6.

Configuring IPv6 Routing and Routing Protocols: This section shows how to configure IPv6 routing and routing protocols on Cisco routers.

IPv6 Transition Options: This section explains some of the options for migrating from IPv4 to IPv6.

IP version 6 (IPv6), the replacement protocol for IPv4, is well known for a couple of reasons. IPv6 provides the ultimate solution for the problem of running out of IPv4 addresses in the global Internet by using a 128-bit address—approximately 10³⁸ total addresses, versus the mere (approximate) 4*10⁹ total addresses in IPv4. However, IPv6 has been the ultimate long-term solution for over ten years, in part because the interim solutions, including Network Address Translation/Port Address Translation (NAT/PAT), have thankfully delayed the day in which we truly run out of public unicast IP addresses.

This chapter focuses on IPv6 addressing and routing, in part because the primary motivation for the eventual migration to IPv6 is to relieve the address constraints of IPv4. This chapter also briefly introduces some of the other features of IPv6, as well as explains some of the reasons for the need for IPv6.

"Do I Know This Already?" Quiz

The "Do I Know This Already?" quiz allows you to assess whether you should read the entire chapter. If you miss no more than one of these nine self-assessment questions, you might want to move ahead to the section "Exam Preparation Tasks." Table 17-1 lists the major headings in this chapter and the "Do I Know This Already?" quiz questions covering the material in those headings so that you can assess your knowledge of these specific areas. The answers to the "Do I Know This Already?" quiz appear in Appendix A.

Table 17-1 "Do I Know This Already?" Foundation Topics Section-to-Question Mapping

1. Which of the following is the most likely organization from which an enterprise could obtain an administrative assignment of a block of IPv6 global unicast IP addresses?

2. 1. An ISP

   2. ICANN

   3. An RIR

   4. Global unicast addresses are not administratively assigned by an outside organization.

3. Which of the following is the shortest valid abbreviation for FE80:0000:0000:0100:0000:0000:0000:0123?

4. 1. FE80::100::123

   2. FE8::1::123

   3. FE80::100:0:0:0:123:4567

   4. FE80:0:0:100::123

5. Which of the following answers lists a multicast IPv6 address?

6. 1. 2000::1:1234:5678:9ABC

   2. FD80::1:1234:5678:9ABC

   3. FE80::1:1234:5678:9ABC

   4. FF80::1:1234:5678:9ABC

7. Which of the following answers list either a protocol or function that can be used by a host to dynamically learn its own IPv6 address?

8. 1. Stateful DHCP

   2. Stateless DHCP

   3. Stateless autoconfiguration

   4. Neighbor Discovery Protocol

9. Which of the following help allow an IPv6 host to learn the IP address of a default gateway on its subnet?

10. 1. Stateful DHCP

    2. Stateless RS

    3. Stateless autoconfiguration

    4. Neighbor Discovery Protocol

11. Which of the following are routing protocols that support IPv6?

12. 1. RIPng

    2. RIP-2

    3. OSPFv2

    4. OSPFv3

    5. OSPFv4

13. In the following configuration, this router's Fa0/0 interface has a MAC address of 4444.4444.4444. Which of the following IPv6 addresses will the interface use?

14. ipv6 unicast-routing
    ipv6 router rip tag1
    interface FastEthernet0/0
     ipv6 address 3456::1/64
    

    1. 3456::C444:44FF:FE44:4444

    2. 3456::4444:44FF:FE44:4444

    3. 3456::1

    4. FE80::1

    5. FE80::6444:44FF:FE44:4444

    6. FE80::4444:4444:4444

15. In the configuration text in the previous question, RIP was not working on interface Fa0/0. Which of the following configuration commands would enable RIP on Fa0/0?

16. 1. network 3456::/64

    2. network 3456::/16

    3. network 3456::1/128

    4. ipv6 rip enable

    5. ipv6 rip tag1 enable

17. Which of the following IPv4-to-IPv6 transition methods allows an IPv4-only host to communicate with an IPv6-only host?

18. 1. Dual-stack

    2. 6to4 tunneling

    3. ISATAP tunneling

    4. NAT-PT

Foundation Topics

The world has changed tremendously over the last 10–20 years as a result of the growth and maturation of the Internet and networking technologies in general. Twenty years ago, no global network existed to which the general populace could easily connect. Ten years ago, the public Internet had grown to the point where people in most parts of the world could connect to the Internet, but with most Internet users being the more computer-savvy people. Today, practically everyone seems to have access, through their PCs, handheld devices, phones, or even the refrigerator.

The eventual migration to IPv6 will likely be driven by the need for more addresses. Practically every mobile phone supports Internet traffic, requiring the use of an IP address. Most new cars have the ability to acquire and use an IP address, along with wireless communications, allowing the car dealer to contact the customer when the car's diagnostics detect a problem with the car. Some manufacturers have embraced the idea that all their appliances need to be IP enabled.

Besides the sheer growth in the need for IPv4 addresses, edicts from governmental agencies could drive demand for IPv6. As of this writing, the U.S. government had set a date in 2008 by which all government agencies should be running IPv6 in their core IP networks. Such initiatives can help drive adoption of IPv6.

While the two biggest reasons why networks might migrate to IPv6 are the need for more addresses and mandates from government organizations, at least IPv6 includes some attractive features and migration tools. Some of those advantages are as follows:

• Address assignment features: IPv6 address assignment allows easier renumbering, dynamic allocation, and recovery of addresses, with nice features for mobile devices to move around and keep their IP address (thereby avoiding having to close and reopen an application).

• Aggregation: IPv6's huge address space makes for much easier aggregation of blocks of addresses in the Internet.

• No need for NAT/PAT: Using publicly registered unique addresses on all devices removes the need for NAT/PAT, which also avoids some of the application layer and VPN-tunneling issues caused by NAT.

• IPsec: IPsec works with both IPv4 and IPv6, but it is required on IPv6 hosts, so you can rely on support for IPsec as needed for VPN tunneling.

• Header improvements: While it might seem like a small issue, the IPv6 header improves several things compared to IPv4. In particular, routers do not need to recalculate a header checksum for every packet, reducing per-packet overhead. Additionally, the header includes a flow label that allows easy identification of packets sent over the same single TCP or User Datagram Protocol (UDP) connection.

• Transition tools: As is covered in the last major section of this chapter, IPv6 has many tools to help with the transition from IPv4 to IPv6.

The worldwide migration from IPv4 to IPv6 will not be an event, or even a year on the calendar. Rather, it will be a long process, a process that has already begun. Network engineers have a growing need to learn more about IPv6. This chapter covers the basics of IPv6, ending with some discussions about the issues of living in a world in which both IPv4 and IPv6 will likely coexist for quite a long time.

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NOTE - Information Week (http://www.informationweek.com) published an interesting article about the need to migrate to IPv6, around the time this book was being completed. To see the article, search the website for the article "The Impending Internet Address Shortage."

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