Our company has successfully used freeswan IPSEC VPN to accomplish this task. We have several installations that have as many as 20 IPSEC VPNs in place as well as PPTP connections.
In some builds of SME we have experienced problems with PPTP connections breaking the IPSEC and forcing a restart of IPSEC, and have never been able to figure out why. Some builds seem to never experience the problem. My opinion has always been that it was a NIC driver issue, but still, we never located it.
But, in general, we have been very successful with freeswan. We installed freeswan from their site.
Larry