A quick overview of the IP filter

This open-source software package provides firewall functionality as well as network address translation to a number of Unix-like operating systems. FreeBSD, NetBSD, OpenBSD, and Solaris are all supported by this open-source firewall. As a kernel loadable module, IPfilter comes with the basic FreeBSD installation. 

The following tutorials will help you troubleshoot IPFilter by providing helpful commands and techniques.

So let’s get start,

First,

Launch IPfilter 

# service ipfilter start

Check out the active packet filtering rules

# ipfstat -io

Remove all filtering rules from the ruleset

ipf -F a

Turn off IPfilter 

# service ipfilter stop

Simple tasks

Permitting SSH but denying everything else

Include the following in /etc/ipf.conf to set up a firewall that blocks everything except SSH on port 22. The example IP address is 11.1.1.5

block in on any all
pass in quick on any proto tcp from any to 11.1.1.5/24 port = 22 keep state

That’s it, We hope this guide was informative for you.

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