Always a bone of contention during the ISA firewall days, the problem still exists for those running TMG firewalls. How do you configure an IPsec tunnel mode site to site VPN between the TMG firewall and an ASA, or whatever Cisco is offering up these days?
The answer can be found on the TechNet wiki!
Check it out at:
DEBRA LITTLEJOHN SHINDER
MVP (Enterprise Security)