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Topic: Networking

Articles, hints, tips, and advice about networking.

O'Reilly Network articles about this topic:

Network Filtering by Operating System (BSD DevCenter)
Some operating systems are better networking citizens than others. Depending on your network, you may want to prioritize traffic from certain machines over traffic from other operating systems--especially when the latest Windows worm strikes. Avleen Vig shows how to use pf, altq, and Squid on FreeBSD to shape your bandwidth with respect to the systems you run.

Building Detailed Network Reports with Netflow (BSD DevCenter)
You can trace every packet on your network from source to destination, if you really want to. Having all of this information is useless unless you can actually find what you need to know. Netflow not only helps record traffic information but also can help you report on just the types of packets you want. Michael W. Lucas demonstrates.

Michal Zalewski on the Wire (ONLamp Security DevCenter)
What motivates a hacker? Perhaps curiosity, the pursuit of knowledge, and the simple joy of saying "Hmm, that's funny! What happens if I ...?" Eccentric security researcher Michal Zalewski exhibits these traits. Fearless interviewer Federico Biancuzzi recently talked with Zalewski about his curious approach to computer security, the need for randomness, and how the hacker mind works.

OpenBSD 3.7: The Wizard of OS (SysAdmin DevCenter)
Has it been six months already? OpenBSD 3.7 is ready to go as you read this. Federico Biancuzzi discusses the release with several core developers, touching on subjects such as Wi-Fi support, improved package tools, and the shipped versions of popular projects including Apache httpd,, and gcc.

Setting up a Secure Subversion Server (SysAdmin DevCenter)
You've finally persuaded your users to stop emailing documents back and forth when they need to collaborate, but you've had to recover three overridden versions on the shared network drive this week. Dru Lavigne has an answer; this month's FreeBSD Basics column demonstrates how to allow users to collaborate on documents with safe and secure version control provided by Subversion.

OpenBSD 3.6 Live (SysAdmin DevCenter)
Right on schedule, the OpenBSD team plans to release version 3.6 on November 1. Federico Biancuzzi recently interviewed several members of the core team about new features and changes in the code and the project.

Secure Your Wireless with IPsec (SysAdmin DevCenter)
Wireless can make your life much, much easier, but those pesky radio waves won't stay put. Sometimes this is good, but sometimes you want to lock down your network. WEP and MAC address filtering aren't secure enough. IPsec, the same approach used to secure VPNs, is much better. Dan Langille explains how to configure Wifi with IPsec.

Building Diskless Clients with FreeBSD 5.2 (SysAdmin DevCenter)
The free Unix-alikes make wonderful thin clients. Having explained how to make a FreeBSD diskless server in Part 1, Mikhail Zakharov demonstrates how to configure FreeBSD diskless clients.

Preventing Denial of Service Attacks (SysAdmin DevCenter)
If you have servers on the public Internet, you're likely vulnerable to external Denial of Service (DoS) attacks. (You may be vulnerable to accidental internal attacks, too.) Fortunately, you can limit their likelihood and severity. Avleen Vig discusses strategies for diagnosing and defending against DoS attacks.

OpenBSD PF Developer Interview, Part 2 (SysAdmin DevCenter)
With the release of OpenBSD 3.5, users and administrators gear up for new features. Federico Biancuzzi interviewed six leading OpenBSD developers responsible for PF, the powerful packet filter, on new features and goals. This is the second half of the interview.

OpenBSD PF Developer Interview (SysAdmin DevCenter)
On the eve of OpenBSD's 3.5 release, users and administrators gear up for new features. Federico Biancuzzi interviewed six leading OpenBSD developers responsible for PF, the powerful packet filter, on new features and goals.

Printing for the Impatient (BSD DevCenter)
While Unix has roots in document formatting and layout, configuring printers has always required more black-arts arcana. This hasn't been helped by the appearance of low-cost commodity WinPrinters. Fortunately, tools like Ghostscript, gimp-print, and Apsfilter make configuring printers much easier. Michael Lucas demonstrates quick and dirty -- and working -- printer configuration.

Improving User Passwords with apg (BSD DevCenter)
The biggest security weakness in any system is usually its users. One line of defense is choosing and enforcing a good password policy. The automatic password generator port can help your users create -- and remember -- effective passwords. Dru Lavigne demonstrates its use and configuration.

Expanding Small NetBSD Systems (BSD DevCenter)
Now that you have NetBSD installed on your palmtop, what will you do with it? Customizing and enhancing the installation can be tricky, but what if you had access to much more disk space? Michael Lucas explains how to enhance your palmtop experience with NFS support, so you can build and install software.

Cleaning and Customizing Your Ports (BSD DevCenter)
One of FreeBSD's biggest benefits is its ports collection. It seems like magic, but a little maintenance can make it work even better for your system. Dru Lavigne explains how to keep your ports collection clean and how to customize individual ports.

portupgrade (BSD DevCenter)
One of FreeBSD's biggest benefits is its ports collection. Perhaps the most important ports utility is portupgrade. Dru Lavigne demonstrates how you can get the most out of your ports collection.

Ports Tricks (BSD DevCenter)
One of FreeBSD's biggest benefits is its ports collection. You can go years without learning more than just make install clean, but there are dozens of features built into the ports tools. Dru Lavigne demonstrates several of these tricks to simplify your life.

SMTP Proxies (BSD DevCenter)
Now that you know all about proxies, you're ready to install and use an SMTP proxy. Why would you want to? To make your life easier. Dru Lavigne explores messagewall, a flexible SMTP proxy.

HTTP Proxies (BSD DevCenter)
Now that you know all about proxies, you're ready to install and use an HTTP proxy. Dru Lavigne explores Squid and Middleman, two effective and powerful HTTP proxies.

Proxy Terminology 101 (BSD DevCenter)
You're probably reading this page through a proxy right now. You might be saving bandwidth, sharing an external IP address, or being protected from work-unsafe material, but could you tell a reverse proxy from an arp proxy? Dru Lavigne explains what these and other terms mean in preparation for installing and running proxies.

Configuring a TFTP Server (BSD DevCenter)
TFTP, the Trivial File Transfer Protocol, is ideal for devices such as routers and network-booting machines. With only a bit of EEPROM space and few utilities, how can you upgrade? Dru Lavigne demonstrates how to configure TFTP to serve hardware images.

IPv6, Meet FreeBSD (BSD DevCenter)
Mike DeGraw-Bertsch takes us through the configuration of IPv6 on FreeBSD.

IPsec Tunneling Between FreeBSD Hosts (BSD DevCenter)
IPSec encrypts data at the IP packet level, so insecure applications can be encrypted while travelling over the Internet. Mike DeGraw-Bertsch shows us how to set it up.

Stable SMB (BSD DevCenter)
SMB has recently improved to the point where it is reliable enough for use in production settings. Michael Lucas tells you how to use SMB to access a Windows share from your FreeBSD workstation.

Accessing a Cisco Router (BSD DevCenter)
When you first purchase a Cisco router, you'll need to access the router via its console interface from a serial interface on your computer. Dru Lavigne shows you how to do this from FreeBSD.

IPFilter on OpenBSD (
IPFilter is a firewall widely used by BSD and Solaris. Mike DeGraw-Bertsch explains how to set it up on OpenBSD and explains a basic ruleset.

IPFW Logging (BSD DevCenter)
Firewalls can potentially block huge amounts of traffic. Dru Lavigne shows us how to fine-tune our firewall logs to reveal the traffic that concerns us most.

Dynamic Address Assignment (Linux DevCenter)
Are you still assigning static IP addresses on your network? Terry Dawson explains how dynamic IP address assignment works and helps you understand if it is right for your network.

Getting Connected with 6to4 (
IPv6 is great in theory, but it won't do you much good if you can't get connected. Hubert Feyrer explains the basics of getting connected to IPv6 for BSD and Linux.

Introduction to IPv6 (
You have been told the Internet is running out of IP addresses and all your friends say NAT is the answer, but what is IPv6 and how is it different from what you are using now?

Setting up Wireless Cards on FreeBSD (BSD DevCenter)
Tired of tripping over Ethernet cables stretched across the house? Michael Lucas show us how to configure wireless Ethernet cards on a FreeBSD laptop.

Wireless Networking (BSD DevCenter)
Michael Lucas gives us an overview of wireless networking in FreeBSD.

Examining ICMP Packets (BSD DevCenter)
Dru Lavigne explains how ICMP packets control messages sent between routers and hosts.

Introduction to Socket Programming with PHP (PHP DevCenter)
Daniel Solin uses a game analogy to show how PHP can be used to exchange data between two computers using network sockets.

IP Packets Revealed (BSD DevCenter)
Dru Lavigne finishes up her series on IP packets with a detailed analysis of the packets captured in the previous article.

Capturing TCP Packets (BSD DevCenter)
Want to capture network packets? Dru Lavigne shows how simple the process is and explains how to analyze the captured data.

TCP Protocol Layers Explained (BSD DevCenter)
Dru Lavigne explains how to read IP packet headers.

Where Have All the IPs Gone? (
There are over 4 billion IP addresses available, and yet, we are still running out. Michael Lucas explains where they went and how people are working to solve the problem.

IPv6: An Interview with Itojun (
Hubert Feyrer interviews Jun-ichiro "itojun" Hagino, one of the core IPv6 developers involved with the KAME project.

Dividing Your Data (BSD DevCenter)
Dru Lavigne walks through the process of setting up partitions in FreeBSD and helps you divide your data into logical storage units.

Creating Network Diagrams (Linux DevCenter)
As the complexity of your network grows, it makes good sense to maintain documentation that describes it. Terry Dawson reviews tools to make this easier.

Monitoring Unix Logins (BSD DevCenter)
Dru Lavigne exposes the contents of wtmp, utmp, and lastlog, the files that record who is logged in to your Unix system.

Securing BSD Daemons (BSD DevCenter)
Dru Lavigne shows us how to secure daemon processes by turning off the ones we don't use and using TCP wrappers to limit access.

Understanding BSD Daemons (BSD DevCenter)
Dru Lavigne introduces the basics of FreeBSD network connections.

Establishing Good Password Policies (BSD DevCenter)
Everyone knows secure passwords are important, but what makes a password secure? Dru Lavigne gives us some tips on creating secure passwords, and shows how to implement a password policy that requires users to create passwords securely.

Fine Control of Ports (BSD DevCenter)
Michael Lucas continues his developer's tour through the ports system and explains how to set the more common variables.

Adding Users to FreeBSD (BSD DevCenter)
Adding users to your Unix system is one of the most important things you can do after the initial setup. Dru Lavigne takes us through the steps of adding a user to a FreeBSD machine.

PalmOS, Half-Life Server, and Ethereal Vulnerabilities (Linux DevCenter)
Problems this week include more symlink problems with catman and dialog, buffer overflows in oops, halflifeserver, and ethereal, key problems with gnupg, problems with PalmOS devices, and a prime example of amazing vulnerabilities in third-party software packages.

BSD Ports Collection Basics (BSD DevCenter)
Michael Lucas takes us on a developers tour through the BSD ports collection. He introduces how the ports collection works and identifies some of its key components.

A Look Through the Ports Collection (BSD DevCenter)
Dru Lavigne looks through the ports collection for interesting and obscure applications.

BSD Tricks: Unprepared Disaster Recovery (BSD DevCenter)
Michael Lucas takes us through every network administrator's nightmare -- a server crash. He documents an actual crash and tells what he did to get things back online.

Security Alerts: Twig, Midnight Commander, and More (Linux DevCenter)
Noel Davis summarizes published open source and Unix exploits. Problems this week include arbitrary code execution in Twig, new symlink attacks, a hidden control code attack on Midnight Commander, and a LANGUAGE attack on glibc.

OpenBSD as a File Server (BSD DevCenter)
David Jorm shows us how OpenBSD makes the perfect file server for cross-platform client networks, including Windows, Macintosh and Unix as well as for complex internetworks.

Security Alerts: OpenBSD Non-exploit and More (Linux DevCenter)
Noel Davis reviews the published exploits from Unix and open source. This week's Insecurities column includes a satirical non-exploit against OpenBSD

Laptops, PC Cards, and FreeBSD (BSD DevCenter)
Michael Lucas shows us how to connect a BSD laptop to the network using a PC Card NIC.

Customizing mrtg (BSD DevCenter)
Part II in setting up BSD as a network status monitoring system using mrtg. Michael Lucas shows us how to custom tailor the mrtg reports.

Long-Term Monitoring with SNMP (BSD DevCenter)
Michael Lucas shows us how to use mrtg to turn long-term SNMP statistics into easy-to-read web pages. It will even chart bar graphs.

OpenBSD and the Future of the Internet (BSD DevCenter)
David Jorm shows us how to setup OpenBSD to use IPv6.

Networking with TCP/IP (BSD DevCenter)
Dru explains the basics of TCP/IP networking and gives examples of how to use it on FreeBSD. This also makes great reading for Linux and other operating systems that utilize the TCP/IP networking stack.

Using Ethereal (BSD DevCenter)
Wondering what's going on with your network? Dru explains how to use Ethereal, a graphical network monitoring package that is easy to use and understand. Learn how to capture packets and monitor network traffic.

Talk the SNMP Talk (BSD DevCenter)
Michael Lucas continues the lesson in SNMP by configuring the SNMP daemon. Practical security measures are also discussed.

OpenBSD in a Datacenter Scale Environment (BSD DevCenter)
David Jorm details an actual installation of OpenBSD in the wild and how it survives powering a high profile site.

Walk the SNMP Walk (BSD DevCenter)
An introduction to the Simple Network Management Protocol and some of its uses as a data collection tool.

Setting Up a Firewall Under OpenBSD (BSD DevCenter)
A tutorial on the basic components that make up a firewall and how to set them up.

Operating Network Services Under OpenBSD (BSD DevCenter)
Learn how to configure the basic network services for a Mail and Web Server.

Connecting to the Internet (Linux DevCenter)
This week's column shows where to get the latest Linux documentation for connecting to the Internet and how to set up a dial-up connection.

Connecting to the Internet Using PPP or a Cable Modem (BSD DevCenter)
Learn how to connect to the internet with FreeBSD, using either a standard or cable modem. Includes information on recompiling your kernel to activate COM ports.

Introduction to OpenBSD Networking (BSD DevCenter)
Learn how to setup the basic networking features of OpenBSD and turn it into a secure Internet router for your home network.

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