Linux Network Administrators Guide
Table of Contents
1. Purpose and Audience for This Book............................................................................................................1
2. Sources of Information...................................................................................................................................2
2.1. Documentation Available via FTP....................................................................................................3
2.2. Documentation Available via WWW...............................................................................................3
2.3. Documentation Available Commercially.........................................................................................3
2.4. Linux Journal and Linux Magazine..................................................................................................4
2.5. Linux Usenet Newsgroups................................................................................................................4
2.6. Linux Mailing Lists..........................................................................................................................5
2.7. Online Linux Support.......................................................................................................................6
2.8. Linux User Groups............................................................................................................................6
2.9. Obtaining Linux................................................................................................................................7
3. File System Standards....................................................................................................................................9
4. Standard Linux Base....................................................................................................................................10
5. About This Book...........................................................................................................................................11
6. The Official Printed Version........................................................................................................................13
7. Overview........................................................................................................................................................15
8. Conventions Used in This Book...................................................................................................................17
9. Submitting Changes......................................................................................................................................18
10. Acknowledgments.......................................................................................................................................19
10.1. The Hall of Fame..........................................................................................................................19
Chapter 1. Introduction to Networking..........................................................................................................21
1.1. History.........................................................................................................................................................22
1.2. TCP/IP Networks.......................................................................................................................................23
1.2.1. Introduction to TCP/IP Networks................................................................................................23
1.2.2. Ethernets......................................................................................................................................24
1.2.3. Other Types of Hardware.............................................................................................................25
1.2.4. The Internet Protocol...................................................................................................................27
1.2.5. IP Over Serial Lines.....................................................................................................................28
1.2.6. The Transmission Control Protocol.............................................................................................28
1.2.7. The User Datagram Protocol.......................................................................................................29
1.2.8. More on Ports...............................................................................................................................29
1.2.9. The Socket Library......................................................................................................................30
1.3. UUCP Networks.........................................................................................................................................31
1.4. Linux Networking......................................................................................................................................32
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1.4.1. Different Streaks of Development...............................................................................................32
1.4.2. Where to Get the Code.................................................................................................................33
1.5. Maintaining Your System.........................................................................................................................34
1.5.1. System Security...........................................................................................................................34
Chapter 2. Issues of TCP/IP Networking.......................................................................................................36
2.1. Networking Interfaces...............................................................................................................................37
2.2. IP Addresses...............................................................................................................................................38
2.3. Address Resolution....................................................................................................................................40
2.4. IP Routing...................................................................................................................................................41
2.4.1. IP Networks.................................................................................................................................41
2.4.2. Subnetworks.................................................................................................................................41
2.4.3. Gateways......................................................................................................................................42
2.4.4. The Routing Table.......................................................................................................................43
2.4.5. Metric Values...............................................................................................................................45
2.5. The Internet Control Message Protocol...................................................................................................46
2.6. Resolving Host Names...............................................................................................................................47
Chapter 3. Configuringthe NetworkingHardware........................................................................................48
3.1. Kernel Configuration.................................................................................................................................51
3.1.1. Kernel Options in Linux 2.0 and Higher.....................................................................................51
3.1.2. Kernel Networking Options in Linux 2.0.0 and Higher..............................................................53
3.2. A Tour of Linux Network Devices............................................................................................................57
3.3. Ethernet Installation..................................................................................................................................59
3.3.1. Ethernet Autoprobing...................................................................................................................59
3.4. The PLIP Driver........................................................................................................................................62
3.5. The PPP and SLIP Drivers.......................................................................................................................64
3.6. Other Network Types................................................................................................................................65
Chapter 4. Configuring the Serial Hardware.................................................................................................66
4.1. Communications Software for Modem Links.........................................................................................67
4.2. Introduction to Serial Devices...................................................................................................................68
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4.3. Accessing Serial Devices............................................................................................................................69
4.3.1. The Serial Device Special Files...................................................................................................70
4.4. Serial Hardware.........................................................................................................................................72
4.5. Using the Configuration Utilities..............................................................................................................73
4.5.1. The setserial Command................................................................................................................73
4.5.2. The stty Command.......................................................................................................................75
4.6. Serial Devices and the login: Prompt.......................................................................................................78
4.6.1. Configuring the mgetty Daemon.................................................................................................78
Chapter 5. Configuring TCP/IP Networking.................................................................................................81
5.1. Mounting the /proc Filesystem.................................................................................................................82
5.2. Installing the Binaries................................................................................................................................83
5.3. Setting the Hostname.................................................................................................................................84
5.4. Assigning IP Addresses..............................................................................................................................85
5.5. Creating Subnets........................................................................................................................................86
5.6. Writing hosts and networks Files.............................................................................................................87
5.7. Interface Configuration for IP..................................................................................................................89
5.7.1. The Loopback Interface...............................................................................................................89
5.7.2. Ethernet Interfaces.......................................................................................................................91
5.7.3. Routing Through a Gateway........................................................................................................92
5.7.4. Configuring a Gateway................................................................................................................93
5.7.5. The PLIP Interface.......................................................................................................................93
5.7.6. The SLIP and PPP Interfaces.......................................................................................................94
5.7.7. The Dummy Interface..................................................................................................................94
5.7.8. IP Alias........................................................................................................................................95
5.8. All About ifconfig.......................................................................................................................................96
5.9. The netstat Command...............................................................................................................................99
5.9.1. Displaying the Routing Table......................................................................................................99
5.9.2. Displaying Interface Statistics...................................................................................................100
5.9.3. Displaying Connections.............................................................................................................101
5.10. Checking the ARP Tables.....................................................................................................................102
Chapter 6. Name Service and Resolver Configuration...............................................................................104
6.1. The Resolver Library..............................................................................................................................105
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6.1.1. The host.conf File......................................................................................................................105
6.1.1.1. Resolver environment variables.................................................................................106
6.1.2. The nsswitch.conf File...............................................................................................................107
6.1.3. Configuring Name Server Lookups Using resolv.conf..............................................................109
6.1.4. Resolver Robustness..................................................................................................................111
6.2. How DNS Works......................................................................................................................................112
6.2.1. Name Lookups with DNS..........................................................................................................113
6.2.2. Types of Name Servers..............................................................................................................114
6.2.3. The DNS Database.....................................................................................................................115
6.2.4. Reverse Lookups........................................................................................................................116
6.3. Running named........................................................................................................................................118
6.3.1. The named.boot File..................................................................................................................118
6.3.2. The BIND 8 host.conf File.........................................................................................................120
6.3.3. The DNS Database Files............................................................................................................121
6.3.4. Caching−only named Configuration..........................................................................................125
6.3.5. Writing the Master Files............................................................................................................126
6.3.6. Verifying the Name Server Setup..............................................................................................128
6.3.7. Other Useful Tools.....................................................................................................................130
Chapter 7. Serial Line IP................................................................................................................................132
7.1. General Requirements.............................................................................................................................133
7.2. SLIP Operation........................................................................................................................................134
7.3. Dealing with Private IP Networks..........................................................................................................137
7.4. Using dip...................................................................................................................................................138
7.4.1. A Sample Script.........................................................................................................................138
7.4.2. A dip Reference.........................................................................................................................140
7.4.2.1. The modem commands..............................................................................................140
7.4.2.2. The echo command....................................................................................................141
7.4.2.3. The get command.......................................................................................................141
7.4.2.4. The print command....................................................................................................141
7.4.2.5. Variable names..........................................................................................................141
7.4.2.6. The if and goto commands.........................................................................................142
7.4.2.7. send, wait, and sleep..................................................................................................142
7.4.2.8. mode and default........................................................................................................142
7.5. Running in Server Mode.........................................................................................................................144
Chapter 8. The Point−to−Point Protocol......................................................................................................146
8.1. PPP on Linux............................................................................................................................................147
8.2. Running pppd...........................................................................................................................................148
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