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`Second Edition
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`Craig Hunt
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`cammdge
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`' Kggcebogfi’sisEx’hi$333048?621 17%”0
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`TCP/IP Network Administration, Second Edition
`by Craig Hunt
`
`Copyright © 1998, 1992 Craig Hunt. All rights reserved.
`Printed in the United States of America.
`
`Published by O’Reilly 8: Associates, Inc, 101 Morris Street, Sebastopol, CA 95472.
`
`Editor: Mike Loukides
`
`Update Editor: Gigi Estabrook
`
`Production Editor: Nicole Gipson Arigo
`
`Printing History:
`
`August 1992:
`
`First Edition.
`
`March 1993:
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`Minor corrections
`
`September 1993: Minor corrections.
`
`January 1994:
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`Minor corrections.
`
`May 1994;
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`Minor corrections.
`
`january 1998:
`
`Second Edition.
`
`Nutshell Handbook and the Nutshell Handbook logo are registered trademarks and The
`javaTM Series is a trademark of O’Reilly 8: Associates, Inc. The association of a crab and the
`topic of TCP/iP is a trademark of O’Reilly 8: Associates, Inc.
`
`Many of the designations used by manufacturers and sellers to distinguish their products are
`claimed as trademarks. Where those designations appear in this book, and O‘Reilly &
`Associates, Inc. was aware of a trademark claim, the designations have been printed in caps
`or initial caps.
`
`While every precaution has been taken in the preparation of this book, the publisher assumes
`no responsibility for errors or omissions, or for damages resulting from the use of the
`information contained herein.
`
`03
`{2&9
`
`This book is printed on acid—free paper With 85% recycled content, 15% post—consumer waste.
`O’Reilly & Associates is committed to using paper with the highest recycled content available
`consistent with high quality.
`
`ISBN: 156592322”
`
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`Table of Contents
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`Preface ................................................................................................................... .. xi
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`1: Overview of TCP/IP ..................................................................... .: .......... .. I
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`TCP/IP and the Internet ................................................................................... .i 2
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`A Data Communications Model ...................................................................... .. 5
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`TCP/IP Protocol Architecture ........................................................................... .. 8
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`Network Access Layer .................................................................................... .. 11
`Internet Layer .................................................................................................. .. 1]
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`Transport Layer ............................................................................................... i. I 7
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`Application Layer ............................................................................................ .. 21
`Summary ......................................................................................................... .. 22
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`2: Delivering the Data ................................................................................ .. 23
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`Addressing, Routing, and Multiplexing ......................................................... .. 23
`The IP Address ............................................................................................... .i 25
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`Subnets ............................................................................................................ .. 31
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`Internet Routing Architecture ........................................................................ .. 34
`
`The Routing Table .......................................................................................... .. 36
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`Address Resolution ......................................................................................... .. 39
`Protocols, Ports, and Sockets ......................................................................... .. 42
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`Summary ......................................................................................................... .. 47
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`vi
`Table of Contents
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`3: Network Services .................................................................................... .. 48
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`Names and Addresses .................................................................................... .. 49
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`The Host Table ............................................................................................... .. 50
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`Domain Name Service .................................................................................... .. 52
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`Mail Services ................................................................................................... .. 60
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`Configuration Servers ..................................................................................... .. 71
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`Bootstrap Protocol .......................................................................................... .. 73
`File and Print Servers ..................................................................................... .4 76
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`Summary ......................................................................................................... .. 78
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`4: Getting Started ......................................................................................... .. 80
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`Connected and Non—Connected Networks ................................................... .. 81
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`Basic Information ........................................................................................... .. 83
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`Planning Routing ............................................................................................ .. 91
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`Planning Naming Service ............................................................................... .. 94
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`Other Services ................................................................................................. .. 97
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`Informing the Users ..................................................................................... .. 100
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`netconfig .....................................................
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`................................................ .. 102
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`Summary ....................................................................................................... .. 104
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`5: Basic Configuration ............................................................................ .. 105
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`Kernel Configuration .................................................................................... .. 105
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`Linux Kernel Configuration ......................................................................... .. 106
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`The BSD Kernel Configuration File ............................................................. .r 112
`The Internet Daemon ................................................................................... .. 118
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`Summary ....................................................................................................... .. 121
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`6: Configuring the Interface .................................................................. .. 123
`
`r The ifconfig Command ................................................................................ .. 123
`TCP/IP Over a Serial Line .................................................
`........................ .. 137
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`Installing PPP ................................................................................................ .. 140
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`Installing SLIP ............................................................................................... .. 153
`Summary ....................................................................................................... .. 162
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`7: Configuring Routing ........................................................................... .. 164
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`Common Routing Configurations ................................................................ .. 164
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`The Minimal Routing Table ......................................................................... .. 165
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`Building 3 Static Routing Table ................................................................... .. I67
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`Interior Routing Protocols ............................................................................ .. 173
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`Exterior Routing Protocols ........................................................................... .. I84
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`Gateway Routing Daemon ........................................................................... .. 187
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`Configuring gated ......................................................................................... .. 189
`Summary ....................................................................................................... .. 200
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`8: Configuring DNS Name Service ...................................................... .. 202
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`BIND: UNIX Name Service .......................................................................... .i 202
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`Configuring the Resolver ............................................................................. .. 205
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`Configuring named ...................................................................................... H 208
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`Using nslookup ............................................................................................ .. 221
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`Summary ....................................................................................................... .. 225
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`9: Configuring Network Servers .......................................................... .. 226
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`The Network File System ............................................................................. .. 226
`Line Printer Daemon .................................................................................... .. 240
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`Network Information Service ....................................................................... .. 245
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`.............. .. 250
`A BOOTP Server ..........................................................................
`DHCP ............................................................................................................ .. 258
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`Managing Distributed Servers ...................................................................... .. 263
`Mail Servers .................................................................................................. .r 266
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`Summary ....................................................................................................... .. 269
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`10: sendmnz'l .................................................................................................. .. 2 7]
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`sendmail’s Function ...................................................................................... .. 272
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`Running sendmail as a Daemon .................................................................. .. 273
`sendmail Aliases ........................................................................................... .. 274
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`The sendmailcf File ..................................................................................... .. 276
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`sendmail Configuration ................................................................................ .. 283
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`Rewriting the Mail Address .......................................................................... .. 295
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`Modifying a sendmailcf File ........................................................................ .. 304
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`Testing serrdmailcf ....................................................................................... .. 308
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`Summary ....................................................................................................... .. 318
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`I 1: Troubleshooting TCP/IP ...............................................
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`.................... .. 319
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`Approaching a Problem ............................................................................... r. 320
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`Diagnostic Tools ........................................................................................... .. 322
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`Testing Basic Connectivity ........................................................................... .. 324
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`Troubleshooting Network Access ................................................................ .. 328
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`Checking Routing ......................................................................................... .. 335
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`Checking Name Service ............................................................................... .. 341
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`viii
`Table of Contents
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`Analyzing Protocol Problems ...................................................................... .. 349
`Protocol Case Study ..................................................................................... .. 352
`Simple Network Management Protocol
`...................................................... .. 356
`Summary ....................................................................................................... .. 36]
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`12: Network Security .................................................................................. .. 362
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`Security Planning .......................................................................................... .. 363
`User Authentication ...................................................................................... .. 368
`Application Security ..................................................................................... .. 384
`Security Monitoring ...................................................................................... .. 385
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`Access Control .............................................................................................. .. 393
`Encryption .................................................................................................... .. 396
`Firewalls ........................................................................................................ .. 398
`Words to the Wise ........................................................................................ .. 403
`Summary ....................................................................................................... .. 404
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`13: Internet Information Resources ..................................................... l. 405
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`The World Wide Web ................................................................................... .. 405
`Anonymous FTP ........................................................................................... .. 408
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`Finding Files ................................................................................................. .. 413
`Retrieving RFCs ............................................................................................ .. 417
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`Mailing Lists .................................................................................................. .. 420
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`The White Pages .......................................................................................... .i 423
`Summary ....................................................................................................... i. 428
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`A: PPP Tools ................................................................................................. .. 429
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`B: A gated Reference ................................................................................. .i 449
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`C: A named Reference .............................................................................. .. 497
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`D: A dbcpd Reference ................................................................................ .. 519
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`E: A sendmdz‘l Reference ......................................................................... .. 532
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`F: Selected TCP/IP Headers .................................................................... .. 583
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`Index .................................................................................................................. .. 589
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