A network manager wants to securely connect a new remote site to the existing headquarters site using a VPN technology that meets security requirements. Which VPN technology should be used?

GRE is a tunneling protocol that provides no encryption or authentication on its own, making it unsuitable when security requirements must be met.

IPsec provides a robust suite of security services - including data confidentiality via encryption (AES), data integrity via HMAC, and peer authentication via IKE - making it the standard choice for site-to-site VPN connectivity between a headquarters and a remote site. It operates at Layer 3 and can secure traffic transparently between two fixed endpoints without requiring client software on end hosts.

Remote-access VPN is designed for individual mobile users connecting to a corporate network, not for permanent site-to-site connectivity.

L2TP provides tunneling at Layer 2 but has no built-in encryption; it typically relies on IPsec for security, making it a more complex and less direct choice than IPsec alone.