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CCNP 1: Advanced IP Addressing Management

Chapter Description

This guide from Cisco Press explains the ins and outs of IP management, including how to resolve IP addressing crises, and how and when to use helper addresses.


Upon completing this chapter, you will be able to

  • Create and configure IPv4 addresses

  • Understand and resolve IP addressing crises

  • Assign a VLSM addressing scheme

  • Configure route summarization

  • Configure private addressing and NAT

  • Use IP unnumbered

  • Understand and configure DHCP and Easy IP

  • Know when to use helper addresses

  • Understand the concepts of IPv6

You can reinforce your understanding of the objectives covered in this chapter by opening the interactive media activities on the CD accompanying this book and performing the lab activities collected in the Cisco Networking Academy Program CCNP 1: Advanced Routing Lab Companion. Throughout this chapter, you will see references to these activities by title and by icon. They look like this:

Interactive Media Activity

Lab Activity

A scalable network requires an addressing scheme that allows for growth. However, several unanticipated consequences can result from unmanaged network growth. As new nodes and networks are added to the enterprise, existing addresses might need to be reassigned. Excessively large routing tables might slow down older routers, and the supply of available addresses might simply run out. You can avoid these unpleasant consequences with careful planning and deployment of a scalable network addressing system.

Network designers can choose from among many different network protocols and addressing schemes. However, with the emergence of the Internet and its nonproprietary protocol, Transmission Control Protocol/Internet Protocol (TCP/IP), this has meant that virtually every enterprise must implement an IP addressing scheme. In addition to TCP/IP, several proprietary network protocols and addressing schemes have been used. Companies such as Apple and Novell have recently migrated their network software to TCP/IP and away from their proprietary protocols. Presently, many organizations choose to run TCP/IP as the only routed protocol on the network. The bottom line is that administrators must find ways to scale their networks by using IP addressing.

Unfortunately, the architects of TCP/IP could not have predicted that their protocol would eventually sustain a global network of information, commerce, and entertainment. Twenty years ago, IP version 4 (IPv4) offered an addressing strategy that, although scalable for a time, resulted in an inefficient allocation of addresses. Over the past two decades, engineers have successfully modified IPv4 so that it can survive the Internet's exponential growth. Meanwhile, an even more extensible and scalable version of IP, IP version 6 (IPv6), has been defined and developed. Today, IPv6 is slowly being implemented in select networks. Eventually, IPv6 might replace IPv4 as the dominant Internet protocol.

This chapter explores the evolution and extension of IPv4, including the key scalability features that engineers have added to it over the years:

  • Subnetting

  • Classless interdomain routing (CIDR)

  • Variable-length subnet masking (VLSM)

  • Route summarization

Finally, this chapter examines advanced IP implementation techniques such as the following:

  • IP unnumbered

  • Dynamic Host Configuration Protocol

  • Helper addresses

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