Linux Network Administrator's Guide

This book, which is one of the most successful to come from the Linux Documentation Project and remains freely distributable under its license, touches on all the essential networking software included with the operating system, plus some hardware considerations. Fully updated, the book now covers firewalls, including the use of ipchains and iptables (netfilter), masquerading, and accounting. Other new topics include Novell (NCP/IPX) support and INN (news administration). Original material on serial connections, UUCP, routing and DNS, mail and News, SLIP and PPP, NFS, and NIS has been thoroughly updated. Kernel options reflect the 2.2 kernel. However, some topics covered in other books (notably Samba and Web server administration) are not in this book.

Topics include:

• Introduction to TCP/IP
• Configuring network and serial hardware
• Domain Name Service
• Serial line communications using SLIP and PPP
• NIS and NFS
• Taylor UUCP
• Administering electronic mail, including smail and sendmail
• Administering Netnews, including INN and several news readers
• Firewalling using ipfwadm, ipchains, and iptables (netfilter)
• Masquerading and accounting
• IPX configuration for a Novell Netware network

Table of contents

Preface

Chapter 1. Introduction to Networking
History
TCP/IP Networks
UUCP Networks
Linux Networking
Maintaining Your System

Chapter 2. Issues of TCP/IP Networking
Networking Interfaces
IP Addresses
Address Resolution
IP Routing
The Internet Control Message Protocol
Resolving Host Names

Chapter 3. Configuring the Networking Hardware
Kernel Configuration
A Tour of Linux Network Devices
Ethernet Installation
The PLIP Driver
The PPP and SLIP Drivers
Other Network Types

Chapter 4. Configuring the Serial Hardware
Communications Software for Modem Links
Introduction to Serial Devices
Accessing Serial Devices
Serial Hardware
Using the Configuration Utilities
Serial Devices and the login: Prompt

Chapter 5. Configuring TCP/IP Networking
Mounting the /proc Filesystem
Installing the Binaries
Setting the Hostname
Assigning IP Addresses
Creating Subnets
Writing hosts and networks Files
Interface Configuration for IP
All About ifconfig
The netstat Command
Checking the ARP Tables

Chapter 6. Name Service and Resolver Configuration
The Resolver Library
How DNS Works
Running named

Chapter 7. Serial Line IP
General Requirements
SLIP Operation
Dealing with Private IP Networks
Using dip
Running in Server Mode

Chapter 8. The Point-to-Point Protocol
PPP on Linux
Running pppd
Using Options Files
Using chat to Automate Dialing
IP Configuration Options
Link Control Options
General Security Considerations
Authentication with PPP
Debugging Your PPP Setup
More Advanced PPP Configurations

Chapter 9. TCP/IP Firewall
Methods of Attack
What Is a Firewall?
What Is IP Filtering?
Setting Up Linux for Firewalling
Three Ways We Can Do Filtering
Original IP Firewall (2.0 Kernels)
IP Firewall Chains (2.2 Kernels)
Netfilter and IP Tables (2.4 Kernels)
TOS Bit Manipulation
Testing a Firewall Configuration
A Sample Firewall Configuration

Chapter 10. IP Accounting
Configuring the Kernel for IP Accounting
Configuring IP Accounting
Using IP Accounting Results
Resetting the Counters
Flushing the Ruleset
Passive Collection of Accounting Data

Chapter 11. IP Masquerade and Network Address Translation
Side Effects and Fringe Benefits
Configuring the Kernel for IP Masquerade
Configuring IP Masquerade
Handling Name Server Lookups
More About Network Address Translation

Chapter 12. Important Network Features
The inetd Super Server
The tcpd Access Control Facility
The Services and Protocols Files
Remote Procedure Call
Configuring Remote Login and Execution

Chapter 13. The Network Information System
Getting Acquainted with NIS
NIS Versus NIS+
The Client Side of NIS
Running an NIS Server
NIS Server Security
Setting Up an NIS Client with GNU libc
Choosing the Right Maps
Using the passwd and group Maps
Using NIS with Shadow Support

Chapter 14. The Network File System
Preparing NFS
Mounting an NFS Volume
The NFS Daemons
The exports File
Kernel-Based NFSv2 Server Support
Kernel-Based NFSv3 Server Support

Chapter 15. IPX and the NCP Filesystem
Xerox, Novell, and History
IPX and Linux
Configuring the Kernel for IPX and NCPFS
Configuring IPX Interfaces
Configuring an IPX Router
Mounting a Remote NetWare Volume
Exploring Some of the Other IPX Tools
Printing to a NetWare Print Queue
NetWare Server Emulation

Chapter 16. Managing Taylor UUCP
UUCP Transfers and Remote Execution
UUCP Configuration Files
Controlling Access to UUCP Features
Setting Up Your System for Dialing In
UUCP Low-Level Protocols
Troubleshooting
Log Files and Debugging

Chapter 17. Electronic Mail
What Is a Mail Message?
How Is Mail Delivered?
Email Addresses
How Does Mail Routing Work?
Configuring elm

Chapter 18. Sendmail
Introduction to sendmail
Installing sendmail
Overview of Configuration Files
The sendmail.cf and sendmail.mc Files
Generating the sendmail.cf File
Interpreting and Writing Rewrite Rules
Configuring sendmail Options
Some Useful sendmail Configurations
Testing Your Configuration
Running sendmail
Tips and Tricks

Chapter 19. Getting Exim Up and Running
Running Exim
If Your Mail Doesn't Get Through
Compiling Exim
Mail Delivery Modes
Miscellaneous config Options
Message Routing and Delivery
Protecting Against Mail Spam
UUCP Setup

Chapter 20. Netnews
Usenet History
What Is Usenet, Anyway?
How Does Usenet Handle News?

Chapter 21. C News
Delivering News
Installation
The sys File
The active File
Article Batching
Expiring News
Miscellaneous Files
Control Messages
C News in an NFS Environment
Maintenance Tools and Tasks

Chapter 22. NNTP and the nntpd Daemon
The NNTP Protocol
Installing the NNTP Server
Restricting NNTP Access
NNTP Authorization
nntpd Interaction with C News

Chapter 23. Internet News
Some INN Internals
Newsreaders and INN
Installing INN
Configuring INN: the Basic Setup
INN Configuration Files
Running INN
Managing INN: The ctlinnd Command

Chapter 24. Newsreader Configuration
tin Configuration
trn Configuration
nn Configuration

Appendix A. Example Network: The Virtual Brewery

Appendix B. Useful Cable Configurations

Index