IPsec VPN on linux ?

Update : I was able to use shrewsoft VPN to make it work. At first I tried to match the config and guessing the config, but I found this tool recently, ike-scan, and it can scan an IP address and found most of the settings. You can also use openswan or strongswan, but you need the version that allow ikev1. Side note, I planned to "NAT" the VPN so I could share the route on my network, creating a sort of site-2-site. Since the protocol use IPsec the NAT rules I used with most SSL VPN didn't work. I was never able to make it work so I downloaded Virtualbox and used the NAT network interface in virtualbox and another interface in the lan network, activating routing on the VM and created a NAT. To my surprise it work incredible well for my needs. (Basically the mating is handle by a nested Linux VM and the VPN is connected on the host. The traffic enter by the nested VM, routed to nat network created by virtualbox and finally transferred on the VPN interface on the host.)