Which of the following is not a type of overlay VPN technology?

The correct choice indicates that L2TP VPN is not considered an overlay VPN technology. Overlay VPN technologies are those that create a virtual network on top of an existing physical network, allowing for encapsulation and encapsulated traffic to traverse through various types of underlying networks.

L2TP, or Layer 2 Tunneling Protocol, is primarily used to support virtual private networks (VPNs) but is often regarded as a tunneling protocol rather than a true overlay technology. It typically requires either IPSec or another encryption method for security since it does not provide encryption on its own. As such, it can be classified more as a tunneling mechanism that establishes a point-to-point connection rather than a full overlay solution.

In contrast, GRE (Generic Routing Encapsulation), IPSec VPN, and SSL VPN are regarded as overlay technologies. GRE encapsulates a wide variety of protocols inside a point-to-point connection, establishing a tunnel that allows for the transmission of various types of traffic. IPSec adds a layer of security to the GRE tunnels, making it also an overlay option. SSL VPN operates over HTTPS to provide secure access to network resources, effectively creating a virtual network for users.

Understanding the distinction between tunneling protocols and full overlay VPN technologies is crucial in networking