IPFilter
free packet filtering and NAT software
IPFilter (commonly referred to as ipf) is an open-source software package that provides firewall services and network address translation (NAT) for many Unix-like operating systems. The author and software maintainer is Darren Reed. IPFilter supports both IPv4 and IPv6 protocols, and is a stateful firewall.
IPFilter is delivered with FreeBSD, NetBSD, Solaris 10 through 11.3, illumos (OpenIndiana) and HP-UX. It used to be a part of OpenBSD, but it was removed by Theo de Raadt in May 2001 due to problems with its license. It was subsequently replaced in OpenBSD by PF, which was developed by OpenBSD's own developers. DragonFly BSD removed its support for IPFilter in May 2011. Oracle Solaris imported the PF firewall from OpenBSD in the 11.3 release, and removed IPFilter in the 11.4 release.
IPFilter can be installed as a runtime-loadable kernel module or directly incorporated into the operating system kernel, depending on the specifics of each kernel and user preferences. The software's documentation recommends the module approach, if possible.
The public source identifies “IPFilter” as free packet filtering and NAT software. This brief keeps that definition visible, then builds a research path around IPFilter, free and packet.
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The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Aug 15, 2026. The linked authority identifier is Q1654315. The first chronological checks are 2001 and 2011.
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This entry incorporates text from “IPFilter” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.