On Sat, 15 Dec 2001 Philip S Tellis wrote :
>
> Mr. Ambrish Kumar took the next lecture on IPSec,
> touching on
> implementations in windows and linux. There were some
> doubts as to
> whether the linux kernel has built in IPSec
> compatibility or if it
> requires a recompile. Maybe someone on the list can
> shed some light on
> this.

No.Current Linux kernel does not have built in IPSec compatibility,because of the US regulation(NSA can decrypt upto only 64-bit encryption).IPSec allows much better and easy encryption than anybody can decrypt.

Some Distrubutions made outside the US like Polish distribution does provide inbuilt IPSec.

I have recompiled the Linux(2.4.12) with Freeswan-IPSec(1.91) and currently using it with 2048-bit RSA encryption for my VPN network.It gives me descent(and the most secure) performance over the cable connection.

See follwing site for more info.
http://www.freeswan.org/