Linux Network Administrators Guide

Linux Network Administrators Guide

source:  http://tldp.org/LDP/nag2/index.html     last updated 24Feb/2018

• Preface

  1. Purpose and Audience for This Book

  2. Sources of Information

  3. File System Standards

  4. Standard Linux Base

  5. About This Book

  6. The Official Printed Version

  7. Overview

  8. Conventions Used in This Book

  9. Submitting Changes

  10. Acknowledgments

  1. Introduction to Networking

  1.1. History

  1.2. TCP/IP Networks

  1.3. UUCP Networks

  1.4. Linux Networking

  1.5. Maintaining Your System

  2. Issues of TCP/IP Networking

  2.1. Networking Interfaces

  2.2. IP Addresses

  2.3. Address Resolution

  2.4. IP Routing

  2.5. The Internet Control Message Protocol

  2.6. Resolving Host Names

  3. Configuringthe NetworkingHardware

  3.1. Kernel Configuration

  3.2. A Tour of Linux Network Devices

  3.3. Ethernet Installation

  3.4. The PLIP Driver

  3.5. The PPP and SLIP Drivers

  3.6. Other Network Types

  4. Configuring the Serial Hardware

  4.1. Communications Software for Modem Links

  4.2. Introduction to Serial Devices

  4.3. Accessing Serial Devices

  4.4. Serial Hardware

  4.5. Using the Configuration Utilities

  4.6. Serial Devices and the login: Prompt

  5. Configuring TCP/IP Networking

  5.1. Mounting the /proc Filesystem

  5.2. Installing the Binaries

  5.3. Setting the Hostname

  5.4. Assigning IP Addresses

  5.5. Creating Subnets

  5.6. Writing hosts and networks Files

  5.7. Interface Configuration for IP

  5.8. All About ifconfig

  5.9. The netstat Command

  5.10. Checking the ARP Tables

  6. Name Service and Resolver Configuration

  6.1. The Resolver Library

  6.2. How DNS Works

  6.3. Running named

  7. Serial Line IP

  7.1. General Requirements

  7.2. SLIP Operation

  7.3. Dealing with Private IP Networks

  7.4. Using dip

  7.5. Running in Server Mode

  8. The Point-to-Point Protocol

  8.1. PPP on Linux

  8.2. Running pppd

  8.3. Using Options Files

  8.4. Using chat to Automate Dialing

  8.5. IP Configuration Options

  8.6. Link Control Options

  8.7. General Security Considerations

  8.8. Authentication with PPP

  8.9. Debugging Your PPP Setup

  8.10. More Advanced PPP Configurations

  9. TCP/IP Firewall

  9.1. Methods of Attack

  9.2. What Is a Firewall?

  9.3. What Is IP Filtering?

  9.4. Setting Up Linux for Firewalling

  9.5. Three Ways We Can Do Filtering

  9.6. Original IP Firewall (2.0 Kernels)

  9.7. IP Firewall Chains (2.2 Kernels)

  9.8. Netfilter and IP Tables (2.4 Kernels)

  9.9. TOS Bit Manipulation

  9.10. Testing a Firewall Configuration

  9.11. A Sample Firewall Configuration

  10. IP Accounting

  10.1. Configuring the Kernel for IP Accounting

  10.2. Configuring IP Accounting

  10.3. Using IP Accounting Results

  10.4. Resetting the Counters

  10.5. Flushing the Ruleset

  10.6. Passive Collection of Accounting Data

  11. IP Masquerade and Network Address Translation

  11.1. Side Effects and Fringe Benefits

  11.2. Configuring the Kernel for IP Masquerade

  11.3. Configuring IP Masquerade

  11.4. Handling Name Server Lookups

  11.5. More About Network Address Translation

  12. ImportantNetwork Features

  12.1. The inetd Super Server

  12.2. The tcpd Access Control Facility

  12.3. The Services and Protocols Files

  12.4. Remote Procedure Call

  12.5. Configuring Remote Loginand Execution

  13. The Network Information System

  13.1. Getting Acquainted with NIS

  13.2. NIS Versus NIS+

  13.3. The Client Side of NIS

  13.4. Running an NIS Server

  13.5. NIS Server Security

  13.6. Setting Up an NIS Client with GNU libc

  13.7. Choosing the Right Maps

  13.8. Using the passwd and group Maps

  13.9. Using NIS with Shadow Support

  14. The NetworkFile System

  14.1. Preparing NFS

  14.2. Mounting an NFS Volume

  14.3. The NFS Daemons

  14.4. The exports File

  14.5. Kernel-Based NFSv2 Server Support

  14.6. Kernel-Based NFSv3 Server Support

  15. IPX and the NCP Filesystem

  15.1. Xerox, Novell, and History

  15.2. IPX and Linux

  15.3. Configuring the Kernel for IPXand NCPFS

  15.4. Configuring IPX Interfaces

  15.5. Configuring an IPX Router

  15.6. Mounting a Remote NetWare Volume

  15.7. Exploring Some of the Other IPX Tools

  15.8. Printing to a NetWare Print Queue

  15.9. NetWare Server Emulation

  16. ManagingTaylor UUCP

  16.1. UUCP Transfers and Remote Execution

  16.2. UUCP Configuration Files

  16.3. Controlling Access to UUCP Features

  16.4. Setting Up Your System for Dialing In

  16.5. UUCP Low-Level Protocols

  16.6. Troubleshooting

  16.7. Log Files and Debugging

  17. Electronic Mail

  17.1. What Is a Mail Message?

  17.2. How Is Mail Delivered?

  17.3. Email Addresses

  17.4. How Does Mail Routing Work?

  17.5. Configuring elm

  18. Sendmail

  18.1. Introduction to sendmail

  18.2. Installing sendmail

  18.3. Overview of Configuration Files

  18.4. The sendmail.cf and sendmail.mc Files

  18.5. Generating the sendmail.cf File

  18.6. Interpreting and Writing Rewrite Rules

  18.7. Configuring sendmail Options

  18.8. Some Useful sendmail Configurations

  18.9. Testing Your Configuration

  18.10. Running sendmail

  18.11. Tips and Tricks

  19. Getting EximUp and Running

  19.1. Running Exim

  19.2. If Your Mail Doesn't Get Through

  19.3. Compiling Exim

  19.4. Mail Delivery Modes

  19.5. Miscellaneous config Options

  19.6. Message Routing and Delivery

  19.7. Protecting Against Mail Spam

  19.8. UUCP Setup

  20. Netnews

  20.1. Usenet History

  20.2. What Is Usenet, Anyway?

  20.3. How Does Usenet Handle News?

  21. C News

  21.1. Delivering News

  21.2. Installation

  21.3. The sys File

  21.4. The active File

  21.5. Article Batching

  21.6. Expiring News

  21.7. Miscellaneous Files

  21.8. Control Messages

  21.9. C News in an NFS Environment

  21.10. Maintenance Tools and Tasks

  22. NNTP and thenntpd Daemon

  22.1. The NNTP Protocol

  22.2. Installing the NNTP Server

  22.3. Restricting NNTP Access

  22.4. NNTP Authorization

  22.5. nntpd Interaction with C News

  23. Internet News

  23.1. Some INN Internals

  23.2. Newsreaders and INN

  23.3. Installing INN

  23.4. Configuring INN: the Basic Setup

  23.5. INN Configuration Files

  23.6. Running INN

  23.7. Managing INN: The ctlinnd Command

  24. Newsreader Configuration

  24.1. tin Configuration

  24.2. trn Configuration

  24.3. nn Configuration

  A. Example Network:The Virtual Brewery

  A.1. Connecting the Virtual Subsidiary Network

  B. Useful Cable Configurations

  B.1. A PLIP Parallel Cable

  B.2. A Serial NULL Modem Cable

  C. Linux Network Administrator's Guide, Second Edition Copyright Information

  C.1. 0. Preamble

  C.2. 1. Applicability and Definitions

  C.3. 2. Verbatim Copying

  C.4. 3. Copying in Quantity

  C.5. 4. Modifications

  C.6. 5. Combining Documents

  C.7. 6. Collections of Documents

  C.8. 7. Aggregation with Independent Works

  C.9. 8. Translation

  C.10. 9. Termination

  C.11. 10. Future Revisions of this License

  D. SAGE: The SystemAdministrators Guild

  Index

  List of Tables

  2-1. IP Address Ranges Reserved for Private Use

  4-1. setserial Command-Line Parameters

  4-2. stty Flags Most Relevant to Configuring Serial Devices

  7-1. Linux Slip-Line Disciplines

  7-2. /etc/diphosts Field Description

  9-1. Common Netmask Bit Values

  9-2. ICMP Datagram Types

  9-3. Suggested Uses for TOS Bitmasks

  13-1. Some Standard NIS Maps and Corresponding Files

  15-1. XNS, Novell, and TCP/IP Protocol Relationships

  15-2. ncpmount Command Arguments

  15-3. Linux Bindery Manipulation Tools

  15-4. nprint Command-Line Options

  List of Figures

  1-1. The three steps of sending a datagram from erdos to quark

  2-1. Subnetting a class B network

  2-2. A part of the net topology at Groucho Marx University

  3-1. The relationship between drivers, interfaces, and hardware

  6-1. A part of the domain namespace

  9-1. The two major classes of firewall design

  9-2. The stages of IP datagram processing

  9-3. FTP server modes

  9-4. A simple IP chain ruleset

  9-5. The sequence of rules tested for a received UDP datagram

  9-6. The rules flow for a received TCP datagram for ssh

  9-7. The rules flow for a received TCP datagram for telnet

  9-8. Datagram processing chain in IP chains

  9-9. Datagram processing chain in netfilter

  11-1. A typical IP masquerade configuration

  15-1. IPX internal network

  16-1. Interaction of Taylor UUCP configuration files

  20-1. Usenet newsflow through Groucho Marx University

  21-1. News flow through relaynews

  23-1. INN architecture (simplified for clarity)

  A-1. The Virtual Brewery and Virtual Winery subnets

  A-2. The Virtual Brewery Network

  B-1. Parallel PLIP cable

  B-2. Serial NULL-Modem cable

  List of Examples

  4-1. Example rc.serial setserial Commands

  4-2. Output of setserial -bg /dev/ttyS Command

  4-3. Example rc.serial stty Commands

  4-4. Example rc.serial stty Commands Using Modern Syntax

  4-5. Output of stty -a Command

  4-6. Sample /etc/mgetty/mgetty.config File

  6-1. Sample host.conf File

  6-2. Sample nsswitch.conf File

  6-3. Sample nsswitch.conf File Using an Action Statement

  6-4. An Excerpt from the named.hosts File for the Physics Department

  6-5. An Excerpt from the named.hosts File for GMU

  6-6. An Excerpt from the named.rev File for Subnet 12

  6-7. An Excerpt from the named.rev File for Network 149.76

  6-8. The named.boot File for vlager

  6-9. The BIND 8 equivalent named.conf File for vlager

  6-10. The named.ca File

  6-11. The named.hosts File

  6-12. The named.local File

  6-13. The named.rev File

  7-1. A Sample dip Script

  12-1. A Sample /etc/inetd.conf File

  12-2. A Sample /etc/services File

  12-3. A Sample /etc/protocols File

  12-4. A Sample /etc/rpc File

  12-5. Example ssh Client Configuration File

  13-1. Sample ypserv.securenets File

  13-2. Sample nsswitch.conf File

  18-1. Sample Configuration File vstout.smtp.m4

  18-2. Sample Configuration File vstout.uucpsmtp.m4

  18-3. Rewrite Rule from vstout.uucpsmtp.m4

  18-4. Sample aliases File

  18-5. Sample Output of the mailstats Command

  18-6. Sample Output of the oststat Command