Foundation Summary

8 Mar

The “Foundation Summary” section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on your exam, a wellprepared candidate should, at a minimum, know all the details in each “Foundation Summary” before going to take the exam.

The three layers of a hierarchy are as follows:
■ The access layer
■ The distribution layer
■ The core layer
Queuing techniques that are manually configured with access lists are as follows:
■ Priority queuing
■ Custom queuing
■ Class-based weighted fair queuing (CBWFQ)
■ Low-latency queuing (LLQ)
Table 3-4 outlines the IP address ranges reserved for private addressing, as specified in RFC 1918.
Table 3-4 Private Address Ranges

Private Address Ranges

To translate one network address into another, the process must differentiate between the
functionality of the addresses being translated. Table 3-5 lists the categories of functions.
Table 3-5 Categories of Functions

Categories of Functions

Figure 3-8 illustrates the use of NAT terms.

120 Chapter 3: Designing IP Networks
Figure 3-8 Using the NAT Terms

IPv6 provides the following features to allow IP networks to scale in a way that IPv4 could not:
■ 128-bit address —The increased address space is a fundamental feature of IPv6. The address has been increased from 32 bits in IPv4 to 128 bits in IPv6.
■ The new header —The new format increases efficiency in routing. The 64-bit alignment of the fields means the packets are processed at higher speeds. Unnecessary fields have been removed, further streamlining the routing process. A new extension header has been added for optional fields.

■ Autoconfiguration —This eliminates the need for DHCP servers and manual IP addressing, thus easing network administration and reducing the volume of network errors due to misconfiguration. Not only is end system address acquisition automated, but it also allows for the network to be renumbered or readdressed without visiting each end system for reconfiguration.
■ Security and mobility —These are built into the protocol specification, as opposed to being configurable options. Both security and mobility are enhanced by the ability to have end-to-end connectivity because of the greater address space available.
■ Transitioning from an IPv4 network —Transitioning an organization is still complex, requiring much consideration. However, transitioning schemes have been carefully thought through and integrated into the protocol functionality. Two of the most common methods include:

— Dual stack
— 6to4 or manually configured tunneling

IPv6 offers the following benefits and features:

■ Larger address space, allowing for a larger number of systems that can be globally addressed and a more scalable network
■ Increased address space, allowing for a deeper hierarchical structure
■ Simplified header, allowing for greater routing efficiency and thus network performance
■ Policies for network architecture flexibility, allowing evolution and growth of the protocol
■ Support for routing and route aggregation
■ Simple administration through serverless autoconfiguration, the ability to renumber with ease, and multihoming, all of which allow a level of plug-and-play support
■ Security using IP Security (IPSec) support for all IPv6 devices
■ Support for Mobile IP and mobile computing devices (direct-path)
■ Multicast support built into the protocol using a greater number of addresses and efficient mechanisms


As mentioned in the introduction, “All About the CCNP, CCDP, and CCIP Certifications,” you have two choices for review questions. The questions that follow next give you a bigger challenge than the exam itself by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better and prove your conceptual and factual knowledge of this chapter. The answers to these questions are found in Appendix A.

For more practice with examlike question formats, including questions using a router simulator and multichoice questions, use the exam engine on the CD.

1. What is an Inside Global address, and when is it used?
2. When is the Inside Local address used?
3. Explain the difference between the Outside Global address and the Outside Local address.
4. Give one example of when NAT might be employed.
5. Explain what PAT is.
6. Why is NAT often configured on the organization’s firewall?
7. Give one example of when private addressing would be a good solution for an organization.
8. Why does summarization need a hierarchical addressing structure?
9. When might you use Destination Address Rotary Translation?
10. Why do NAT and private addressing tend to be implemented together?
11. Which routing protocols for IPv6 does Cisco IOS support?
12. How many bits are there in the IPv6 address space?
13. Explain why it is important to remember to identify how many hosts and subnets are required when designing an IPv4 network.
14. Why does IPv6 addressing allow for more effective security and QoS to be implemented?
15. Give one reason it might be advisable to implement private addressing.
16. In the following address
which part of the address is autoconfigured?
17. Why is IPv6 multicasting more efficient than IPv4 broadcasting?
18. State one of the main benefits of IPv6.
19. What is an IPv6 extension header?
20. What are the two most common methods of transitioning an IPv4 network to an IPv6 network?

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