We always knew that different VPN gateway vendors went out of their way to loosely interpret RFC in order to lock out other VPN gateway vendors, so that customers would have to buy the same vendor's VPN gateway for each office. Among the vendors that seemed to go to out of their way in this area is Cisco.
Well, they decided to completely close the door on interoperability this month -- so if you want to connect your ISA firewall VPN gateway to an ASA, then you're going to have to do it without Cisco's help or support.
For more information, check out Joe Harris' blog post here:
(Many thanks to Adrian Dimcev from www.carbonwind.net for pointing out this issue)
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer