Which of the following IPv6 transition technologies is used by the DirectAccess if a user is in a remote location and a public IPv4 address, instead of public IPv6 address, has been assigned to the co

ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) is designed to transmit IPv6 packets within an intranet over an IPv4 infrastructure, not for external DirectAccess clients with public IPv4 addresses.

PortProxy is a Windows netsh command used to forward TCP connections between addresses and ports, not an IPv6 transition or encapsulation technology.

6to4 is an IPv6 transition mechanism that automatically encapsulates IPv6 packets within IPv4 packets using protocol 41. DirectAccess selects 6to4 specifically when the client machine is assigned a public (globally routable) IPv4 address, because 6to4 requires a public IPv4 address to construct the 6to4 relay address. This distinguishes it from Teredo, which is reserved for clients behind NAT.

Teredo encapsulates IPv6 over UDP to traverse NAT devices, so DirectAccess uses it only when the client is behind NAT with a private IPv4 address, not a public one.