TCP/IP Network Administration: Help for Unix System Administratorsby Craig Hunt
This complete guide to setting up and running a TCP/IP network is essential for network administrators, and invaluable for users of home systems that access the Internet. The book starts with the fundamentals -- what protocols do and how they work, how addresses and routing are used to move data through the network, how to set up your network connection -- and then
This complete guide to setting up and running a TCP/IP network is essential for network administrators, and invaluable for users of home systems that access the Internet. The book starts with the fundamentals -- what protocols do and how they work, how addresses and routing are used to move data through the network, how to set up your network connection -- and then covers, in detail, everything you need to know to exchange information via the Internet.Included are discussions on advanced routing protocols (RIPv2, OSPF, and BGP) and the gated software package that implements them, a tutorial on configuring important network services -- including DNS, Apache, sendmail, Samba, PPP, and DHCP -- as well as expanded chapters on troubleshooting and security. TCP/IP Network Administration is also a command and syntax reference for important packages such as gated, pppd, named, dhcpd, and sendmail.With coverage that includes Linux, Solaris, BSD, and System V TCP/IP implementations, the third edition contains:
- Overview of TCP/IP
- Delivering the data
- Network services
- Getting startedM
- Basic configuration
- Configuring the interface
- Configuring routing
- Configuring DNS
- Configuring network servers
- Configuring sendmail
- Configuring Apache
- Network security
- Appendices include dip, ppd, and chat reference, a gated reference, a dhcpd reference, and a sendmail reference
Don't Lose the Tree in the Forest
In 1991, when Hunt wrote the first edition of TCP/IP Network Administration, TCP/IP nodes were scattered across the country like occasional trees dotting a rolling cow pasture. While about 600,000 computers were on the Internet in 1991, most UNIX systems were host-centric -- one central computer serving only terminals and printers via RS232. Also, among the connected computers, TCP/IP only gave us boring things like e-mail, ftp, and telnet. There wasn't a virtual world of animated graphics and hi-fi sound to lure the game-drunk masses to the Net. Networked home PCs were rare enough to warrant raised eyebrows. The relatively few networked PCs were not using TCP/IP. Netware was king in the DOS world and UNIX-to-UNIX-Copy (UUCP) ruled the underworld of UNIX. Like the few TCP/IP nodes themselves, Hunt's subject was one lone tree in a pasture. You actually knew what to expect when you bought the first edition -- a book describing TCP/IP on a UNIX system.
The world changed. A book on TCP/IP can now discuss CGI, HTTP, NT, HTML, WINS, and a multitude of other letters that have absolutely nothing to do with administering a UNIX network. Now, installing TCP/IP can range from a thirteen-year-old installing Netscape on her father's computer to a college network administrator connecting heterogeneous UNIX machines to heterogeneous networks. A rain forest of trees sprang up around Hunt's one lone tree.
Hunt might have lost sight of his tree in such a forest. Thankfully for the rest of us, he resisted. The second edition is only an update of the first. He discusses sendmail 8.8.5 instead of version 5.6.5. He also discusses the latest versions of bind, Linux, and Solaris. He added Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP) to the routing section. The information is updated, but his style and craft are the same. His focus is still sharp, his writing is still clear, and his organization is still logical. While the book has no practical value to the UNIX-free, it quietly replaces its predecessor in the UNIX required reading list for the rest of us.
Hunt is very practical in his advice. This book is a handbook for the handyman, not the speculations of a scientist. For example, when discussing troubleshooting, Hunt gives the following advice: check the cables, keep good records, keep an open mind, duplicate the problem, and keep your speculations to yourself. It sounds like he has done this before. Hunt's greatest strength is his practicality borne from years of experience.
Hunt starts briefly with the theoretical, but spends the majority of the book on the practical execution. This structure works very well. You get an overview of the subject before learning a selected tricks. It's always good to go once around the elephant before sticking your hand under its foot to remove a thorn. Knowing the size of an elephant is important if your hand is going under its foot.
The first three chapters introduce key concepts like IP headers, IP addresses, subnetting, ports, and services. The next chapter describes planning a network. Hunt discusses the practical issues involved in planning a network: Use hostnames that are easy to spell, use a mail server to collect mail, use an installation planning sheet to document the network, and reorder the planning sheet to match the order of the questions posed by the operating system. The planning chapter documents a fictitious network, nuts.com, that is used for the remainder of the book. The following six chapters are a network configuration tutorial based on the nuts.com network. Hunt then discusses what to do when TPC/IP doesn't work correctly at nuts.com. Then he discusses security at nuts.com. The book finishes with sources of additional information and a few selected reference sections.
The book is not implementation specific. Hunt concentrates on concepts, not release-specific step-by-step instructions. Your OS documentation gives you that information. Hunt compares the different ways UNIX systems are configured. That's important for those of us that are responsible for different flavors of UNIX. For example, chapter 5, the kernel configuration chapter, uses Solaris, Linux, and FreeBSD as examples. Unless you have the same OS version as outlined in the book, you can't configure your kernel with only the information Hunt gives. However, you'll understand the key concepts: Some UNIX systems like Solaris don't trust you to configure the kernel; some systems like Linux strongly encourage you to configure the kernel; a properly configured kernel is more efficient; different OS releases are configured differently. Hunt gives you an overview of kernel configuration without excessive details on configuring a system that you don't have.
Hunt, for the most part, includes everything you'll need to know about the subject without weighing the book down with trivia. I appreciate the unsaid trivia as much as the spoken butt-saving fact. We spend too much of our time reading information that serves no useful purpose. You don't always need to know everything about a subject -- just the important things. Hunt is selective with information. For example, when discussing firewalls, he gives a brief overview of firewalls without telling you how to build one. He ends the firewall discussion with the advice to hire it done unless you have time to kill. Too many authors describe the mountains that line the wrong-turn road.
The important things are usually said. However, I would have included two things that didn't make the final cut of the second edition: Santa Cruz Operation (SCO) specific information and configuring sendmail to occasionally use UUCP. The omission of UUCP is understandable. UUCP, while important to me personally, is not as important to the rest of the world as it was several years ago. The complete omission of SCO from the second edition, which was in the first edition, is not as understandable. SCO now owns the UNIX source code. This was not the case when the first edition was published. This isn't a serious flaw -- just a curious one. SCO systems are configured very much like the included systems. However, there are some differences. For example, the TCP/IP startup files are located in a different script. An SCO system starts TCP/IP in /etc/rc2.d/S85tcp while a Linux system starts it in /etc/rc.d/rc.inet1. Mentioning issues like these would have made a more complete book.
Regardless, Hunt's book is still one of the best UNIX sys admin books ever written. The second edition has all the strengths of the first. Moreover, it still fills a real need, though a different one. When the first edition hit the press, it described the obscure TCP/IP to a UUCP-dominated market. Hunt was an evangelist. Well, the world is converted and we need a tour guide. Hunt is now that tour guide. The second edition gives us a birds-eye-view of the TCP/IP terrain that can't be found in any one system's documentation.--Dr. Dobb's Electronic Review of Computer Books
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Read an Excerpt
Chapter 1: Overview of TCP/IPAll of us who use a UNIX desktop system- engineers, educators, scientists, and business people-have second careers as UNIX system administrators. Networking these computers gives us new tasks as network administrators.
Network administration and system administration are two different jobs. System administration tasks such as adding users and doing backups are isolated to one independent computer system. Not so with network administration. Once you place your computer on a network, it interacts with many other systems. The way you do network administration tasks has effects, good and bad, not only on your system but on other systems on the network. A sound understanding of basic network administration benefits everyone.
Networking computers dramatically enhances their ability to communicate-and most computers are used more for communication than computation. Many mainframes and supercomputers are busy crunching the numbers for business and science, but the number of such systems pales in comparison to the millions of systems busy moving mail to a remote colleague or retrieving information from a remote repository. Further, when you think of the hundreds of millions of desktop systems that are used primarily for preparing documents to communicate ideas from one person to another, it is easy to see why most computers can be viewed as communications devices.
The positive impact of computer communications increases with the number and type of computers that participate in the network. One of the great benefits of TCP/IP is that it provides interoperable communications between all types of hardware and all kinds of operating systems.
This book is a practical, step-by-step guide to configuring and managing TCP/IP networking software on UNIX computer systems. TCP/IP is the software package that dominates UNIX data communications. It is the leading communications software for UNIX local area networks and enterprise intranets, and for the foundation of the worldwide Internet.
The name "TCP/IP" refers to an entire suite of data communications protocols. The suite gets its name from two of the protocols that belong to it: the Transmission Control Protocol and the Internet Protocol. Although there are many other protocols in the suite, TCP and IP are certainly two of the most important.
The first part of this book discusses the basics of TCP/IP and how it moves data across a network. The second part explains how to configure and run TCP/IP on a UNIX system. Let's start with a little history.
TCP/IP and the InternetIn 1969 the Advanced Research Projects Agency (ARPA) funded a research and development project to create an experimental packet-switching network. This network, called the ARPANET, was built to study techniques for providing robust, reliable, vendor- independent data communications. Many techniques of modern data communications were developed in the ARPANET.
The experimental ARPANET was so successful that many of the organizations attached to it began to use it for daily data communications. In 1975 the ARPANET was converted from an experimental network to an operational network, and the responsibility for administering the network was given to the Defense Communications Agency (DCA). However, development of the ARPANET did not stop just because it was being used as an operational network; the basic TCP/IP protocols were developed after the ARPANET was operational.
The TCP/IP protocols were adopted as Military Standards (MIL STD) in 1983, and all hosts connected to the network were required to convert to the new protocols. To ease this conversion, DARPA funded Bolt, Beranek, and Newman (BBN) to implement TCP/IP in Berkeley (BSD) UNIX. Thus began the marriage of UNIX and TCP/IP.
About the time that TCP/IP was adopted as a standard, the term Internet came into common usage. In 1983, the old ARPANET was divided into MILNET, the unclassified part of the Defense Data Network (DDN), and a new, smaller ARPANET. "Internet" was used to refer to the entire network: MILNET plus ARPANET.
In 1985 the National Science Foundation (NSF) created NSFNet and connected it to the then-existing Internet. The original NSFNet linked together the five NSF supercomputer centers. it was smaller than the ARPANET and no faster - 56Kbps. Nonetheless, the creation of the NSFNet was a significant event in the history of the Internet because NSF brought with it a new vision of the use of the Internet. NSF wanted to extend the network to every scientist and engineer in the United States. To accomplish this, in 1987 NSF created a new, faster backbone and a three-tiered network topology that included the backbone, regional networks, and local networks.
In 1990, the ARPANET formally passed out of existence, and the NSFNet ceased its role as a primary Internet backbone network in 1995. Still, today the Internet is larger than ever and encompasses more than 95,000 networks worldwide. This network of networks is linked together in the United States at several major interconnection points:
- The three Network Access Points (NAPs) created by the NSF to ensure continued broad-based access to the Internet.
- The Federal Information Exchanges (FIXs) interconnect U.S. government networks.
- The Commercial Information Exchange (CIX) was the first interconnect specifically for commercial Internet Service Providers (ISPs).
- The Metropolitan Area Exchanges (MAEs) were also created to interconnect commercial ISPs.
The Internet has grown far beyond its original scope. The original networks and agencies that built the Internet no longer play an essential role for the current network. The Internet has evolved from a simple backbone network, through a three-tiered hierarchical structure, to a huge network of interconnected, distributed network hubs. It has grown exponentially since 1983 - doubling in size every year. Through all of this incredible change one thing has remained constant: the Internet is built on the TCP/IP protocol suite.
A sign of the network's success is the confusion that surrounds the term internet. Originally it was used only as the name of the network built upon the Internet Protocol. Now internet is a generic term used to refer to an entire class of networks. An internet (lowercase "i") is any collection of separate physical networks, interconnected by a common protocol, to form a single logical network. The Internet (uppercase "I") is the worldwide collection of interconnected networks, which grew out of the original ARPANET, that uses Internet Protocol (IP) to link the various physical networks into a single logical network. In this book, both "internet" and "Internet" refer to networks that are interconnected by TCP/IP.
Because TCP/IP is required for Internet connection, the growth of the Internet has spurred interest in TCP/IP As more organizations become familiar with TCP/IP they see that its power can be applied in other network applications. The Internet protocols are often used for local area networking, even when the local network is not connected to the Internet. TCP/IP is also widely used to build enterprise networks. TCP/IP-based enterprise networks that use Internet techniques and World Wide Web tools to disseminate internal corporate information are called intranets. TCP/IP is the foundation of all of these varied networks.
TCP/IP FeaturesThe popularity of the TCP/IP protocols did not grow rapidly just because the protocols were there, or because connecting to the Internet mandated their use. They met an important need (worldwide data communication) at the right time, and they had several important features that allowed them to meet this need. These features are:
- Open protocol standards, freely available and developed independently from any specific computer hardware or operating system. Because it is so widely supported, TCP/IP is ideal for uniting different hardware and software, even if you don't communicate over the Internet.
- Independence from specific physical network hardware. This allows TCP/IP to integrate many different kinds of networks. TCP/IP can be run over an Ethernet, a token ring, a dial-up line, an FDDI net, and virtually any other kind of physical transmission medium.
- A common addressing scheme that allows any TCP/IP device to uniquely address any other device in the entire network, even if the network is as large as the worldwide Internet.
- Standardized high-level protocols for consistent, widely available user services.
Protocol StandardsProtocols are formal rules of behavior. In international relations, protocols minimize the problems caused by cultural differences when various nations work together. By agreeing to a common set of rules that are widely known and independent of any nation's customs, diplomatic protocols minimize misunderstandings; everyone knows how to act and how to interpret the actions of others. Similarly, when computers communicate, it is necessary to define a set of rules to govern their communications.
In data communications these sets of rules are also called protocols. In homogeneous networks, a single computer vendor specifies a set of communications rules designed to use the strengths of the vendor's operating system and hardware architecture. But homogeneous networks are like the culture of a single country-only the natives are truly at home in it. TCP/IP attempts to create a heterogeneous network with open protocols that are independent of operating system and architectural differences. TCP/IP protocols are available to everyone, and are developed and changed by consensus-not by the flat of one manufacturer. Everyone is free to develop products to meet these open protocol specifications.
The open nature of TCP/IP protocols requires publicly available standards documents. All protocols in the TCP/IP protocol suite are defined in one of three Internet standards publications. A number of the protocols have been adopted as Military Standards (MIL STD). Others were published as Internet Engineering Notes (IEN) - though the IEN form of publication has now been abandoned. But most information about TCP/IP protocols is published as Requests for Comments (RFCs). RFCs contain the latest versions of the specifications of all standard TCP/IP protocols. As the title "Request for Comments" implies, the style and content of these documents is much less rigid than most standards documents. RFCs contain a wide range of interesting and useful information, and are not limited to the formal specification of data communications protocols.
As a network system administrator, you will no doubt read many of the RFCs yourself. Some contain practical advice and guidance that is simple to understand. Other RFCs contain protocol implementation specifications defined in terminology that is unique to data communications....
Meet the Author
Craig Hunt has worked with computer systems for the last 25 years. He spent the first few years after receiving his B.A. from American University running an outdoor camp for inner-city kids, but the call of the computer was stronger than the call of the wild. Craig went to work for the federal government as a programmer and then as a systems programmer. He left the government to work for Honeywell on the WWMCCS network in the days before TCP/IP, back when the network used NCP. After Honeywell, Craig went to work for the National Institute of Standards and Technology. He's still there today and currently leads the Advanced Network Technologies Division. Craig is a member of the Federal Networking Council, the Large Scale Network Working Group, and the Next Generation Internet Implementation Team. He taught a course on TCP/IP network administration at Montgomery College in the 1980s and currently teaches a tutorial on the subject at Networld+Interop. In addition to TCP/IP Network Administration, he wrote Networking Personal Computers with TCP/IP and Appendix C of Building Internet Firewalls. He is currently working on a version of TCP/IP Network Administration for Windows NT.
Craig lives with his wife and children in Gaithersburg, Maryland. He loves the outdoors, splitting vacation time between the mountains and the sea, and he has a passion for rock and roll music.
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