IP Addressing and Subnetting INC IPV6

Including IPv6

Syngress

• Publisher: Syngress
• Year: 2000
• Print ISBN: 9781928994015
• eBook ISBN: 9780080535227
• Topic: Computer Science
• Subtopic: Computer Science General
• Index: Computer Science

Internetworking Protocol (IP) addresses are the unique numeric identifiers required of every device connected to the Internet. They allow for the precise routing of data across very complex worldwide internetworks. The rules for their format and use are governed by the Internet Engineering Task Force (IETF) of the The Internet SOCiety (ISOC). In response to the exponential increase in demand for new IP addresses, the IETF has finalized its revision on IP addressing as IP Version 6, also know as IPng (ng = Next Generation). Key hardware vendors such as Cisco and major Internet Service Providers such as America Online have already announced plans to migrate to IP Version 6.IP address allocation within an organization requires a lot of long-term planning. This timely publication addresses the administrator and engineer's need to know how IP 6 impacts their enterprise networks. - Easy-to-read, light technical approach to cellular technology - Ideal for companies planning a phased migration from IP 4 to IP 6 - Timely publication: The IETF standard was finalized in early 1999 and will begin to be implemented in late 1999/2000. The current IP Version 4 address set will be exhausted by 2003 - The book focuses on planning and configuring networks and devices for IP 6. Specifically, it will cover how to: Increase the IP address size from 32 bits to 128 bits; Support more levels of addressing hierarchy; Support an increased number of addressable nodes; Support simpler auto-configuration of addresses; Improve the scalability of multicast routing by adding a "scope" field to multicast addresses; Use a new "anycast address" to send a packet to any one of a group of nodes

Chapter 1

Addressing and Subnetting Basics

Solutions in this chapter:

IP Address Basics

Purpose of Subnetting

The Basic Fixed Length Mask

IP Address Basics

IPv4 addressing is used to assign a logical address to a physical device. That sounds like a lot to think about, but actually it is very simple. Two devices in an Ethernet network can exchange information because each of them has a network interface card with a unique Ethernet address that exists in the physical Ethernet network. If device A wants to send information to device B, device A will need to know the Ethernet address of device B. Protocols like Microsoft NetBIOS require that each device broadcast its address so that the other devices may learn it. IP uses a process called the Address Resolution Protocol. In either case, the addresses are hardware addresses and can be used on the local physical network.

For IT Professionals

RFC

In this chapter you will see references to the term RFC. An RFC, Request For Comment, is a document created by the internet community to define processes, procedures, and standards that control how the Internet and associated protocols work. Each RFC is assigned a number and a title that describes the contents. As an example, RFC791 is entitled “Internet Protocol” and is the standard that defines the features, functions, and processes of the IP protocol. RFCs are free and the whole text of any RFC can be downloaded from the Internet. You can find them at the following URL: http://www.isi.edu/in-notes.

As an IT Professional, you may often ask, “Why did they do that?” Since the RFC is the official documentation of the Internet, you can often gain insight into why things are the way they are by reading RFCs related to your question.

What happens if device B, on an Ethernet network, wants to send information to device C on a token-ring network? They cannot communicate directly because they are on different physical networks. To solve the addressing problems of both device A and B, we use a higher layer protocol such as IPv4. IPv4 allows us to assign a logical address to a physical device. No matter what communication method is in use, we can identify a device by a unique logical address that can be translated to a physical address for actual information transfer.

Classful Addressing–Structure and Size of Each Type

The designers of IPv4 faced an addressing dilemma. In the early days of Internet development, networks were small and networking devices were big. Another issue was the future. In the early 1970s, the engineers creating the Internet were not aware of the coming changes in computers and communications. The invention of local area networking and personal computers was to have a momentous impact on future networks. Developers understood their current environment and created a logical addressing strategy based on their understanding of networks at the time.

They knew they needed logical addressing and determined that an address containing 32 bits was sufficient for their needs. As a matter of fact, a 32-bit address is large enough to provide 2³² or 4,294,967,296 individual addresses. Since all networks were not going to be the same size, the addresses needed to be grouped together for administrative purposes. Some groups needed to be large, some of moderate size, and some small. These administrative groupings were called address classes.

For IT Professionals

Addressing

From RFC791, page 7:

“A distinction is made between names, addresses, and routes [4]. A name indicates what we seek. An address indicates where it is. A route indicates how to get there. The internet protocol deals primarily with addresses. It is the task of higher level (i.e., host-to-host or application) protocols to make the mapping from names to addresses. The internet module maps internet addresses to local net addresses. It is the task of lower level (i.e., local net or gateways) procedures to make the mapping from local net addresses to routes. Addresses are fixed length of four octets (32 bits). An address begins with a network number, followed by local address (called the “rest” field). There are three formats or classes of internet addresses: in class a, the high order bit is zero, the next 7 bits are the network, and the last 24 bits are the local address; in class b, the high order two bits are one-zero, the next 14 bits are the network and the last 16 bits are the local address; in class c, the high order three bits are one-one-zero, the next 21 bits are the network and the last 8 bits are the local address.”

IPv4 addresses are expressed in dotted decimal notation. For example, a 32-bit address may look like this in binary:

To make it easier to read, we take the 32-bit address and group it in blocks of eight bits like this:

Finally, we convert each eight-bit block to decimal and separate the decimal values with periods or “dots.” The converted IPv4 address, expressed as a dotted decimal address, is:

126.136.1.47

It is certainly easier to remember that your IP address is 126.136.1.47 instead of remembering a string of bits such as 01111110100010000000000100101111.

What Is a Network?

When talking about IP addressing, it is important to understand what the word “network” means. A network is a group of computing devices connected together by some telecommunications medium. It may be as small as a workgroup in the accounting department or as large as all of the computers in a large company, such as General Motors. From an addressing perspective, all computers in a network come under the administrati...

Table of contents

• Cover image
• Title page
• Table of Contents
• [email protected]
• Copyright
• Acknowledgments
• Contributors
• Preface
• Editor’s Acknowledgments
• Chapter 1: Addressing and Subnetting Basics
• Chapter 2: Creating an Addressing Plan for Fixed-Length Mask Networks
• Chapter 3: Private Addressing and Subnetting Large Networks
• Chapter 4: Network Address Translation
• Chapter 5: Variable-Length Subnet Masking
• Chapter 6: Routing Issues
• Chapter 7: Automatic Assignment of IP Addresses with BOOTP and DHCP Objectives
• Chapter 8: Multicast Addressing
• Chapter 9: IPv6 Addressing
• Chapter 10: The IPv6 Header
• Address Assignment
• Index
• Administering Active Directory