This file is part of the documentation for the Linux FreeS/WAN project.
See the documentation index or project home page for more information.

Linux FreeS/WAN compatibility Guide


Most of this document is quoted directly from the Linux FreeS/WAN mailing list at:
Thanks very much to the community of testers, patchers and commenters there, especially the ones quoted below but also various contributors we haven't quoted.

Implemented parts of the IPSEC Specification

In general, do not expect Linux FreeS/WAN to do everything yet. This is a work-in-progress and some parts of the IPSEC specification are not yet implemented.

In Linux FreeS/WAN

Things we should do, as of version 1.2:

Not (yet) in Linux FreeS/WAN

Things we don't yet do, as of version 1.1:
There is likely to be considerable change in this list for version 1.2. A number of pieces of user-contributed code may be integrated by then.

Intel Linux other than Redhat

We develop and test on: This is what we recommend.

Other 2.0.x Intel Kernels

We strongly recommend 2.0.38.

Various versions of the code have run at various times on most 2.0.xx kernels, but the current version is tested only on 2.0.38 and is unlikely to compile on older kernels. Some of our patches for older kernels are shipped in 2.0.37 and later, so they are no longer provided in FreeS/WAN.

2.2 and 2.3 Kernels

Unlike FreeS/WAN 1.0, version 1.1 will run on Linux 2.2 kernels. FreeS/WAN 1.2 also runs on 2.3 kernels.

Linux distributions other than Redhat

We develop and test on Redhat 5.2 for 2.0 kernels, and on Redhat 6.0 for 2.2, so minor changes may be required for other distributions.

SuSE Linux 5.3

Date: Mon, 30 Nov 1998
From: Peter Onion <>

... I got Saturdays snapshot working between my two SUSE5.3 machines at home.

The mods to the install process are quite simple.  From memory and looking at
the files on the SUSE53 machine here at work....

And extra link in each of the /etc/init.d/rc?.d directories called K35ipsec
which SUSE use to shut a service down.

A few mods in /etc/init.d/ipsec  to cope with the different places that SUSE
put config info, and remove the inculsion of /etc/rc.d/init.d/functions and .
/etc/sysconfig/network as they don't exists and 1st one isn't needed anyway.

insert ". /etc/rc.config" to pick up the SUSE config info and use 

  if test -n "$NETCONFIG" -a "$NETCONFIG" != "YAST_ASK" ; then

to replace 

  [ ${NETWORKING} = "no" ] && exit 0

Create /etc/sysconfig  as SUSE doesn't have one.

I think that was all (but I prob forgot something)....
You may also need to fiddle initialisation scripts to ensure that /var/run/ is removed when rebooting. If this file is present, Pluto does not come up correctly.


Subject: Re: linux-ipsec: Slackware distribution
  Date:  Thu, 15 Apr 1999 12:07:01 -0700
  From:  Evan Brewer <>

> Very shortly, I will be needing to install ipsec on at least gateways that
> are running Slackware. . . .

The only trick to getting it up is that on the slackware dist there is no
init.d directory in /etc/rc.d .. so create one.  Then, what I do is take the
ipsec startup script which normally gets put into the init.d directory, and
put it in /etc/rc.d and name ir rc.ipsec .. then I symlink it to the file
in init.d.  The only file in the dist you need to really edit is the
utils/Makefile, setup4:

Everything else should be just fine.


Subject: FreeS/WAN 1.0 on Debian 2.1
   Date: Tue, 20 Apr 1999
  From:  Tim Miller <>

        Compiled and installed without error on a Debian 2.1 system
with kernel-source-2.0.36 after pointing RCDIR in utils/Makefile to

        /var/lock/subsys/ doesn't exist on Debian boxen, needs to be
created; not a fatal error.

        Finally, ipsec scripts appear to be dependant on GNU awk
(gawk); the default Debian awk (mawk-1.3.3-2) had fatal difficulties.
With gawk installed and /etc/alternatives/awk linked to /usr/bin/gawk
operation appears flawless.
The scripts in question have been modified since this was posted. Awk versions should no longer be a problem.

CPUs other than Intel

Corel Netwinder (StrongARM CPU)

Subject: linux-ipsec: Netwinder diffs
Date: Wed, 06 Jan 1999

I had a mistake in my ipsec-auto, so I got things working this morning.

Following are the diffs for my changes.  Probably not the best and cleanest way 
of doing it, but it works. . . . 

These diffs are in the 0.92 distribution and any snapshot after Feb 20 1999, so these should work out-of-the-box on Netwinder.

Yellow Dog Linux on Power PC

Subject:  Compiling FreeS/WAN 1.1 on YellowDog Linux (PPC)
   Date:  11 Dec 1999
   From:  Darron Froese <>

I'm summarizing here for the record - because it's taken me many hours to do
this (multiple times) and because I want to see IPSEC on more linuxes than
just x86.

Also, I can't remember if I actually did summarize it before... ;-) I'm
working too many late hours.

That said - here goes.

1. Get your linux kernel and unpack into /usr/src/linux/ - I used 2.2.13.

2. Get FreeS/WAN and unpack into /usr/src/freeswan-1.1

3. Get the gmp src rpm from here:

4. Su to root and do this: rpm --rebuild gmp-2.0.2-9a.src.rpm

You will see a lot of text fly by and when you start to see the rpm
recompiling like this:

Executing: %build
+ umask 022
+ cd /usr/src/redhat/BUILD
+ cd gmp-2.0.2
+ libtoolize --copy --force
Remember to add `AM_PROG_LIBTOOL' to `'.
You should add the contents of `/usr/share/aclocal/libtool.m4' to
+ CFLAGS=-O2 -fsigned-char
+ ./configure --prefix=/usr

Hit Control-C to stop the rebuild. NOTE: We're doing this because for some
reason the gmp source provided with FreeS/WAN 1.1 won't build properly on

cd /usr/src/redhat/BUILD/
cp -ar gmp-2.0.2 /usr/src/freeswan-1.1/
cd /usr/src/freeswan-1.1/
rm -rf gmp
mv gmp-2.0.2 gmp

5. Open the freeswan Makefile and change the line that says:
KERNEL=$(b)zimage (or something like that) to

6. cd ../linux/

7. make menuconfig
Select an option or two and then exit - saving your changes.

8. cd ../freeswan-1.1/ ; make menugo

That will start the whole process going - once that's finished compiling,
you have to install your new kernel and reboot.

That should build FreeS/WAN on ydl (I tried it on 1.1).

Alpha 64-bit processors

Subject: IT WORKS (again) between intel & alpha :-)))))
   Date: Fri, 29 Jan 1999
   From: Peter Onion <>

Well I'm happy to report that I've got an IPSEC connection between by intel &
alpha machines again :-))

If you look back on this list to 7th of December I wrote...

-On 07-Dec-98 Peter Onion wrote:
-> I've about had enuf of wandering around inside the kernel trying to find out
-> just what is corrupting outgoing packets...
-Its 7:30 in the evening .....
-I FIXED IT  :-))))))))))))))))))))))))))))))))
-It was my own fault :-((((((((((((((((((
-If you ask me very nicly I'll tell you where I was a little too over keen to
-change unsigned long int __u32 :-)  OPSE ...
-So tomorrow it will full steam ahead to produce a set of diffs/patches against
-Peter Onion.

Subject: Diifs to use a newer version on the des library.
Date: Fri, 29 Jan 1999
From: Peter Onion <>

Inorder to get the alpha version to work you need to use a newer version of the
des library in klips.
. . .
The newer version of the library is in the 0.92 distribution and all snapshots after Feb 20 1999.

Alpha with 2.2.x kernel version

Subject: RE: linux-ipsec: V 2.2.1
   Date: Sun, 31 Jan 1999 10:19:41 +0000 (GMT)
  From: Peter Onion <>

On 31-Jan-99 wrote:
> I am trying to port freeswan to 2.2.1. I can get the patches working, what
> now?  I also have a DEC ALPHA with ver 2.2.1 kernel

Ah !!!!  

Well unless you get the update des library I mentioned the other day, yo can
look forward to corrupt free lists and kernel crashes (In my experience anyway 
This should no longer be a problem since the library has been updated in the distrubution. There will, however, likely still be problems. See below:
Subject: RE: linux-ipsec: V 2.2.1
Date: Sun, 31 Jan 1999 20:53:20 -0500 (EST)
From: Henry Spencer <>

> > I am trying to port freeswan to 2.2.1. I can get the patches working, what
> > now?  I also have a DEC ALPHA with ver 2.2.1 kernel
> Well unless you get the update des library I mentioned the other day, yo can
> look forward to corrupt free lists and kernel crashes...

Unfortunately, if that "2.2.1" means what I think it does, the DES library
is the least of his problems.  Porting FreeS/WAN to the Linux 2.2 kernels
is almost certain to be a major job, involving some redesign, not just a
matter of finding and fixing minor glitches.

Interoperation with other IPSEC implementations

Developers routinely test against some other implementations.

KLIPS, running on an Intel CPU, is tested against OpenBSD 2.3's IPSEC implementation, running on a Sun SPARC machine. Since this is a different implementation on a machine with opposite byte order, this is a good initial test of interoperability.

Pluto is tested against SSH Communications Security's Internet test page.

There are some published interoperability results:

Users have tested against a number of other implementations.


This report is from one of the OpenBSD IPSEC developers, a regular participant on our mailing list:
Subject: spi.c bug
   Date: Tue, 23 Feb 1999
   From: Niklas Hallqvist <>

PS.  I don't know if you have an interop list anywhere, but you should
know FreeS/WAN interops with OpenBSD both at the IPSec level and at
the IKE level.
He has also talked of porting NetBSD's isakmpd(8) to Linux, but has (as of late April '99) made no announcement of availability. This would provide an alternative to our pluto(8) daemon with a somewhat different feature set. Our
KLIPS kernel code would still be used.


The only
reference we have to IPSEC for FreeBSD says their code was ported from OpenBSD. It should therefore interoperate with us, but we have no test results on this.

Cisco Routers

Subject: cisco <-> pluto IKE interop is here........
   Date: Thu, 28 Jan 1999
   From: Ian Calderbank

Ok, tried todays pluto (28 jan) snapshot against a (wait for it) 3des
cisco box, one with some more serious grunt for benchmarking when the time

And the good news is that pluto and cisco's IKE seem to interoperate. At
the end of things both devices seem to be happy that they have IKE and
IPSEC SA's. I can't send any traffic over it cos klips seems to be broken
(peter seems to be on the case), but fundamentally, pluto seems to be
interoperable with cisco for SA negotiation.

I've attached some ipsec barf output - pluto still complains a few times,
but it gets there :-)
A later message from Ian:

This configuration is provided as-is and with no assistance or guarantee
that it works whatsover. In particular your attention is drawn to the versions
of operating systems and IPSEC that were used in the test. Configurations
for later versions of freeswan and cisco IOS may well be different.

Cisco router: 3640 (R4700 processor), ios 12.0(2a)T1), 3DES IPSEC feature set
( you do need the 3des version).
Linux box: P150, freeswan 29/jan/99 snapshot, Redhat 5.2, kernel 2.0.36.
Interconnect: 10 Base T.
Algorithm: ESP 3des/md5

CPU loadings: 
Cisco 3640 : 98%
Freeswan P150 : load average: 0.08, 0.06, 0.01

Throughput: 1.1 Mbit/sec at the application layer, approx 1.2Mbit/sec, 100 packet/sec on 
the external network. There were no chokes present, so the limit would 
appear to be the 3640, given it was running near flat out. 


Freeswan config:

auto    ipsec-router-test
# x.x.x.x = linux box public ip address
# y.y.y.y = router public ip address
# private network behind the router - host to which throughput testing was done is here.


Cisco Router config:

crypto isakmp policy 1
 encr 3des
 hash md5 
 authentication pre-share
crypto isakmp key SECRET-VALUE address x.x.x.x 
crypto ipsec transform-set 3DES-MD5 esp-3des esp-md5-hmac 
crypto map TEST 1 ipsec-isakmp  
 set peer x.x.x.x
 set transform-set 3DES-MD5 
 match address 101
access-list 101 permit ip host x.x.x.x
crypto map TEST

Bay Networks switch

Subject: Re: Interop (was spi.c bug)
   Date: Wed, 24 Feb 1999
   From: Ian Calderbank <>

I've also tested against a Bay (Newoak) Contivity Extranet switch,
running v2.02.

Attempts to connect as a single user client fail completely - to be
expected, they use Aggressive mode and username/password (xauth draft I
suspect, but I can't get confirmation) for that mode, which freeswan
doesn't support yet.

Attemps to connect as a "remote network" - for which bay which uses main
mode, authenticating on IP address and password (certs are also
available), which freeswan ought to have a better chance of working at ,
also fails, however I think that could be down to the fact that my Bay
is a 1DES only box. I don't have time to get the detail of the error
messages together, but the general impressions is that the
authentication is ok and they disagree about policy.

I might be able to get strong crypto for the bay-newoak box, but it will
take me many months, and (I admit to being slightly confused by this)
I've heard it said that their 3des is only 128bit, so perhaps may not
interop with 168 bit?

I don't want to kick off the 1des/3des debate again but it should be
noted that I only got freeswan<->cisco ike/ipsec working when I got hold
of 168bit 3des code for the cisco, and left freeswan unmodified. I never
got the "downgrade to 1des" untested freeswan code mods that Hugh R
suggested on 23/12/98 to work - I gave up on them when I got hold of
3des cisco code. I obviously tried these same mods against the 1des
bay-newoak, but I have no proof that the mods were valid in the first
place, so it could have been an invalid test. Without proven 1des
freeswan code it is difficult for me to test again.
A later report:
Subject: Contivity Extranet Switch
   Date: Fri, 11 Jun 1999
   From: Matthias David Siebler <>
Organization: Nortel Networks

More interoperability results:

I successfully established a tunnel with a Nortel (formerly Bay (formerly New Oak)) Contivity
Extranet Switch running the latest release versions.

The CES is running V2.50 of the software and the Linux server is running V1.0.0 of the Free/SWAN
code on a RedHat 5.2 unit with the kernel upgraded to 2.0.36-3

I am using IKE with 3DES-HMAC-MD5

Note however, that tunnels cannot yet be configured as client tunnels since Free/SWAN does not yet
support aggressive mode.  Hopefully, that will arrive soon, which would allow remote users to
connect to a CES using the Free/SWAN code as clients.

Raptor Firewall on Windows NT

Subject: Interoperability with Raptor 5 (Success!)
   Date: Wed, 06 Jan 1999 16:19:27 -0500
   From: Chuck Bushong <>

I don't know if this is useful information for anyone, but I have
successfully established a VPN between RedHat 5.1 (kernel 2.0.34) running
FreeS/WAN 0.91 and NT4 running Raptor 5.  However, Pluto does not appear
compatible with the Raptor IKE implementation.  Unfortunately, I am not in
control of the Raptor end of the tunnel to be able to continue testing

With full debugging turned on, I'm getting the following messages, but it
isn't preventing anything from working. . . .

Subject: RE: linux-ipsec: Interoperability with Raptor 5 (Success!)
Date: Thu, 28 Jan 1999 17:22:55 -0500
From: Chuck Bushong <>

Sorry.  I don't administer the Raptor box.
The company at the other end would have to incur expense to test it
(They use a consultant).  However, while we are on the subject,
this VPN (at least the klips end) has been up under minimal
utilization for three weeks plus without interruption.  The
machine seems very stable.  Pat yourself on the back, gentlemen.
Your beta release is more stable than certain companies' shipping

Keep up the good work. 

F-Secure VPN for Windows

Subject: linux-ipsec: Identification through other than IP number
   Date: Tue, 13 Apr 1999
   From: Thomas Bellman <>

... Currently we are trying to interop FreeS/WAN
with F-Secure VPN+ Client 4.0 (for MS Windows), and as long as
the Windows machine has a fix IP address, and are initiating the
IKE negotiations, things are working well.  However, when the IP
address is changing, it doesn't work. ...
(I'll try to write something up about the problems we are having
when Pluto is initiatior in another message.)

Xedia Access Point/QVPN

Subject: linux-ipsec: Interoperability result
   Date: Mon, 15 Mar 1999 18:08:12 -0500
  From: Paul Koning <>

Here's another datapoint for the "FreeS/WAN interoperability

I tested 0.92 against the Xedia Access Point/QVPN product, using
dynamic keying (i.e., Pluto at work).

Results: it works fine so long as you ask for 3DES.  DES and no-crypto 
modes don't work when Pluto is involved.

I did limited data testing, which seemed to be fine.  No performance
numbers yet, could do that if people are interested.

Any questions, please ask.


PGP 6.5 Mac and Windows IPSEC Client

Subject: linux-ipsec: PGPnet interoperable with FreeSWAN
   Date: Mon, 05 Apr 1999 18:06:13 -0700
   From: Will Price <>

Network Associates announced PGP 6.5 today.  It includes a new product
PGPnet which is a full IKE/IPSec client implementation.  This product
is for Windows and Macintosh.  I just wanted to send a brief note to
this list that the product was compatibility tested with FreeSWAN
prior to its release, and the tests were successful!

Freeware versions of PGPnet for non-commercial use should be available
by the end of the quarter.  Only the commercial Windows NT version is
available today.  95/98/Mac will be available by the end of the

PGPnet is the first IKE product to support authentication with OpenPGP
keys.  It also supports X.509 certs from VeriSign, NetTools, and
Entrust.  The FreeSWAN interop test was obviously done using Shared

Full source code will of course be made available after we finish all
the builds.  If you'd like more information, we had a lot of press
releases today, and our website has some information although it is
still partially being updated.

- -- 
Will Price, Architect/Sr. Mgr., PGP Client Products
Total Network Security Division
Network Associates, Inc.

IRE Safenet/SoftPK

IRE have an extensive line of IPSEC products, including firewall software with IPSEC and hardware encryption devices for LAN or modem links. Their Soft-PK is a Win 98 and NT client. We have reports only of testing on NT.

Subject: Re: Identification through other than IP number
  Date:  Fri, 23 Apr 1999
  From:  Tim Miller <>

Randy Dees writes:

 > Anyone know of a low-cost MS-Win client that interoperates and does not
 > require purchasing a server license to get it?  

        SafeNet/Soft-PK from IRE ( is a low-cost
client (though I don't have the exact cost available at the moment).
I've got it running on an NT4 workstation and it interoperates nicely
(in transport mode, will try tunnel later) with FreeS/WAN.  It's also
ICSA IPsec certified.

Cerebus <>
A later report from a different user:
Subject: Interop.. testing. WIN32 client : Success Story
   Date: Thu, 11 Nov 1999
   From: Jean-Francois Nadeau <>
You can add IRE's products in the supported, well working (and cheap)
WIN32 client. I tested it (SafeNet SoftPK 3DES) against Freeswan 1.0
and 1.1 in both tunnel and transport mode in a RoadWarrior configuration.  No bug.  
The software is light, non-intrusive and transparent for the user.....defenitly,
thats a good one.
The tunnel is establish on demand. 
Using shared keys....but hope to use certificates with it soon (well,
when Freeswan will ;)).



Subject: ipsec interoperability FYI
   Date: Sun, 02 May 1999
   From: Sean Rooney <>

we've been doing some basic interoperability testing of the following; 

PGP NT VPN 6.5 and freeswan both seem to work reasonably well with 
Borderware 6.0 and freegate 1.3 beta. [as well as eachother] 

more details coming soon. 


Subject: TimeStep Permit/Gate interop works!
   Date: Thu, 10 Jun 1999
   From: Derick Cassidy <>

Just a quick note of success.  TimeStep Permit/Gate (2520) and
Free/Swan (June 4th snapshot) interoperate!

I have them working in AUTO mode, with IKE.  IPSec SA's are negotiated
with 3DES and MD5.

Here are the configs and a diagram for both configs.

left subnet---| Timestep | --- internet --- | Linux box |

The left subnet is defined as the red side of the timestep box.
 This network definition MUST exist in the Secure Map.

On the Linux box:


conn timestep

In the TimeStep permit/gate Secure Map

begin static-map
        target ""
        mode   "ISAKMP-Shared"
        tunnel ""

In the TimeStep Security Descriptor file

begin security-descriptor
        Name    "High"
        IPSec   "ESP 3DES MINUTES 300 or ESP 3DES HMAC MD5 MINUTES 300"
                                or DES MD5 MINUTES 1440"

The timestep has a shared secret for
set in the Shared Secret Authentication tab of Permit/Config.

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