I've been fighting (once every couple of months) with DirectAccess over IPv6 addresses handed out by home routers.
Some staff (mostly Comcast and ATT customers) are getting the addresses, along with an IPv4 address, and when that happens, it's very hit or miss whether the computer at home will connect via DirectAccess. Fortunately, we have a backup SSL VPN unit, so folks can use that as an alternative, but it's not really satisfactory to staff to have to figure out that DirectAccess isn't working and then switch to the SSL VPN. I've googled off and on for a long time (months!), and posted in the appropriate forum on Technet, with no particular resolution. I don't experience it, because Frontier FIOS isn't handing me an IPv6 address, so I can't replicate it directly, and when I get a call from someone who's suffering, they generally don't want to take the time to do the extensive troubleshooting required Frustrating... Any thoughts welcome. Kurt
