How does Iptables work? ….
The short answer is that user-defined tables for packet filtering, nat, packet mangling etc. hook into kernelspace chains (INPUT, OUTPUT, FORWARD, PREROUTING and POSTROUTING. Packets negotiating these kernelspace chains get filtered according to the rules in the tables. You might learn a litle more by clicking through the slides from an Iptables seminar I once gave at Princeton University.
Connection tracking is an area I have become quite interested in. See these posts for more detailed explanations of connection tracking in Iptables:
Connection Tracking – TCP
Connection Tracking – UDP
Connection Tracking – ICMP
Connection Tracking – FTP
Example Rulesets
Iptables example firewall rulesets are available “here”.
If you are keen to get hands on with configuring Iptables, “this post” looks at an affordable way to do it if you don’t already have access to a Linux box. In either case, be prepared to do some traffic analysis in order to debug any problems with the ruleset.
Recommended Reading
Hi All
i want to know how to set up proxy outside a router machine
using iptables..
please help me
Comment by Eko — May 20, 2007 @ 8:31 pm
I sure wish I was at the seminar. I really need to learn Iptables for our corporate servers. Been baffled about it for quite some time now. I’ll still read about your slides, hope I learn a thing or two then Google out some more tutorials.
Thanks for the Slides.
Joe Orchid
http://www.ocalanewcarquote.com
Comment by Joe Orchid — May 29, 2007 @ 2:49 pm
I had an hard time learning how IPTABLES work.. but ur presentation made it look like its a piece of cake…..
thanks so very much………..
i wish i could have attended ur presentation… anyways its never late to learn…
if you have any more of such wonderful presentations…. please post them….
thanks and regards
mayank verma
Comment by Mayank Verma — June 26, 2007 @ 9:33 pm