GRE (Generic Routing Encapsulation) is not specifically considered a VPN technology. While it can be utilized for tunneling traffic across networks, GRE lacks critical VPN features like authentication, encryption, and secure tunneling protocols like L2TP or IPSec. VPNs employ secure tunneling technologies to establish encrypted and authenticated connections, protecting data privacy and network security, whereas GRE is a general-purpose tunneling protocol primarily designed for routing purposes.