After Moving Configuration Backup from ISA (Internet Security and Acceleration) Server 2006 to TMG (Threat Management Gateway) Server 2010, RRAS Service of TMG not responding.

Following error can be viewed on event viewer,
Event 14104,
Microsoft Forefront TMG Firewall
Failed to start the Routing & Remote Access Service. Look at the system event log for more errors

Due to the RRAS (Routing and Remote Access Service) failure, VPN on TMG 2010 does not Work.

Resolution:
Do the following to get RRAS working and the VPN issue will also resolve when RRAS start.

Note:- Before doing any change addition/deletion in registry, must take registry backup. (Back up and Restore Registry in Windows ^[1])

Goto Run

Type Regedit

Browse to
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RemoteAccess\RouterManagers\IPv6

Delete the registry entry
Open Services (Type services.msc on Run)
start the RRAS service
Now check VPN, It will work.