What are the differences between OpenSwan and StrongSwan? All I found is this comparison between the outdated FreeSwan and testing version of OpenSwan - i.e. current stable of OpenSwan is 2.6 (3.0 in comparison) and current stable for StrongSwan is 4.4 (4.1.7 in comparison) which seems grossly unfair (there is no point in comparing Windows 98 with Ubuntu 10.10 or Mac OS X 10.7 with Slackware 8.0).

After reading some websites, StrongSwan seems to be better maintained while OpenSwan seems to be more popular.

  • @Sven my edit was meant to remove irrelevant and outdated stuff (the link is broken by the way) and to broaden the question to a third product (ipsec-tools mentioned in the answer below), but in the end the question stays the same and is still about the differences between the three IPSec stacks. Could you please review the edit again ? Thanks. – user186340 Jan 1 '15 at 12:47
  • @AndréDaniel: No, because I really can't. I also think your edit got too far, as it went way beyond fixing links and retroactively widened the scope of the question. Besides, I think this question is off-topic by todays standard. – Sven Jan 1 '15 at 14:56

NOTE: See the other answer, this one was correct in 2011, but the landscape has changed in that time and this is no longer the correct answer to the OP's question.

Both OpenSwan and StrongSwan are forks for continued development after FreeS/WAN project closed up shop. However, most of the Linux distributions have moved more towards IPsec-Tools since then.

You can use either one for IPsec on Linux, but unless you have a specific need for them, or you are trying to maintain configuration compatibility with older FreeS/WAN setups, you are probably better off using IPsec-Tools and Racoon (ISAKMP daemon from IPsec-Tools) for any new Linux IPSec Setups.

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    Red Hat 6 has moved away from IPSec-Tools and uses OpenSwan now. I still agree with this answer, though. – joechip Jul 29 '11 at 10:38
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    Looks like Ubuntu is moving from IPsec-Tools to StrongSwan in 14.04: wiki.ubuntu.com/TrustyTahr/ReleaseNotes#strongSwan – A B Apr 17 '14 at 21:38
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    As of RHEL7, it looks like the default IPSec system is Libreswan, a fork of OpenSwan. – Christopher Cashell Jul 25 '14 at 16:38
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    @ChristopherCashell you should update your original answer too :) – ismail Aug 24 '14 at 9:38
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    @ChristopherCashell the answer was good in 2011, but now in 2016, Canonical and RedHat present other alternatives for VPN with ipsec, like LibreSwan, OpenSwan and StrongSwan. – Yonsy Solis Jul 11 '16 at 19:21

Libreswan is the project the Openswan developers created after the company they had originally founded to develop Openswan sued them over the trademark. So Libreswan is what we will discuss here.

The most obvious differences are:

Distro support:

  • StrongSwan is the recommended default in Ubuntu since 14.04.
  • RHEL 7 ships Libreswan, though StrongSwan is available in EPEL.

IPSec-tools was a port of the KAME IPSec userland from BSD to Linux. It appears to be no longer maintained.

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    They got sued by Xelerance? Ahh it pays to be a lawyer. Here's an out-take from "Openswan: Building and Integrating VPNs"(PacktPub): "...Openswan was released by Xelerance, a newly founded company for the continued development of a free IPsec implementation for Linux. Openswan's main mission was to cater more to the commercial world, while still keeping the FreeS/WAN ideals alive. This new code-fork also released the FreeS/WAN Project to stick even more strongly to its philosophies...In April 2003, the end of the FreeS/WAN Project was announced..." – ILMostro_7 Oct 24 '15 at 23:25
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    Oh yes. And as is typical of such lawsuits, the company got the trademark, while simultaneously killing the project they were fighting over. Openswan has had only the occasional security patch since then. – Michael Hampton Oct 25 '15 at 0:10

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