iptables notes
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Block an IP (basic, won't survive reboot): iptables -A INPUT -s 123.123.123.123 -j DROP
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A good, easy tutorial on the basics of IPtables.
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http://www.justlinux.com/nhf/Security/IPtables_Basics.html
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I found debugging iptables confusing until I figured out this basic command to list the NAT rules:
- list the NAT rules:
iptables -L -t nat
- list the FILTER rules (default iptables -L):
iptables -L
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Some versions of SmoothWall use iptables.
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iptables has a built in port knocking ability? https://www.adayinthelifeof.nl/2012/03/12/why-putting-ssh-on-another-port-than-22-is-bad-idea/
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Test rules: "Set a “failsafe” on a timer. The at command is great for this. Something simple, like echo 'service iptables stop' | at now + 1min will stop the iptables service after a minute. If you locked yourself out, grab a cup of coffee, log back in, and try again."
Tags: iptables, iptable, firewall, list, port forward, linux router, example, syntax,