Linux Routers: A Book Review

by Ralph Krause

According to the preface, Linux
isn't only about routers, "It's about running
Linux in production and all the nontechnical details which go along
with it." To accomplish this, author Tony Mancill includes
information on Linux itself, routing basics, networking hardware
and details of real-world systems that he has implemented.Mancill is a UNIX systems administrator with Bank of America.
He previously served as a system administrator for LHS
Communications and as a UNIX systems programmer for BellSouth. He
is also a volunteer developer for Debian GNU/Linux.Linux Routers is 345 pages long and
contains eight chapters, appendices, a glossary, bibliography and
an index. The book also contains numerous diagrams, sample scripts,
output from commands and footnotes. The book's examples concentrate
on 2.2.x kernels and the Debian distribution.The first two chapters cover topics applicable to all Linux
routers, such as what type of hardware and operating environments
contribute to reliable system operation. Differences between
full-sized Linux distributions and mini distributions such as LRP,
Trinux and floppyfw are covered. Topics such as IP subnetting,
routing tables and private IP address spaces are discussed. There
are also numerous examples on using base-2 math to manipulate and
mask IP addresses.Chapters Three through Eight deal with routers used and
configured by Mancill for specific situations and detail some of
the things he learned while working on them.The system discussed in Chapter Three routes between
physically separate subnets. This chapter also serves as a
Linux-routing introduction because it explains how to enable IP
forwarding in the kernel, how to configure Ethernet interfaces and
how to use IP aliasing and accounting.The router configurations covered in the later chapters
include using Linux as an extranet router (a router used to connect
your network to other networks, not including the Internet), a
frame-relay router and an internet router.In addition to router configuration, the book contains
information on what IP masquerading is and how to use it,
IP-monitoring tools such as tcpdump and sniffit, port scanners such
as Satan and SAINT and using Sangoma's WANPIPE software. There is
also a discussion about running internet services such as DNS and
Sendmail on a router.Network security measures are discussed in Chapters Six and
Eight. Security topics covered include physical security for the
machines, password security, network service security, firewalling
and proxying. There is a section on how to detect network problems
and have the computer notify you of them and also a section on how
to make your environment more available with information regarding
planning redundant services and servers, using another machine as a
safe place to store such things as configuration files for use in
an emergency and using rescue disks.The appendices contain some information that beginning
network administrators may find beneficial. In addition to sources
of networking and Linux information, Mancill includes guidelines
for testing changes made to systems and keeping track of them. He
also includes personal thoughts on how to convince management to
use Linux and some ethical considerations for a network
administrator.The Prentice Hall web site doesn't contain an errata or
corrections section for this book. The author does include an
e-mail address for feedback or criticisms, however.Linux Routers is organized in clean,
distinct chapters, and the text is easy to follow. There are
numerous explanations, hints and definitions in each chapter and a
glossary to help the reader understand difficult concepts. The book
is geared toward using Linux in a company environment as a reliable
router as well as an economic alternative to dedicated commercial
boxes. While not a beginner's book, there is some information on
topics such as drive partitioning, building a kernel and basic
networking. The examples are all written for the 2.2.x kernel and
the Debian distribution, but this does not detract from the value
of the information presented.Product
Ralph Krause lives in
Michigan and works as a web designer, writer and occasional
programmer. He has been using Linux for three years and is working
to fill all available space in his home with computer

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