Which protocol is MOST likely used to establish an IPSec VPN tunnel?

The correct answer is based on the specific role that ISAKMP plays in establishing an IPSec VPN tunnel. ISAKMP, which stands for Internet Security Association and Key Management Protocol, is a framework that allows for the establishment of security associations and the management of cryptographic keys. It facilitates the negotiation of security parameters needed to set up an IPSec VPN tunnel, such as the encryption and integrity algorithms.

In the context of IPSec, ISAKMP is often used in conjunction with IKE (Internet Key Exchange) to handle the initial setup of the VPN connection. This involves exchanging the necessary parameters to enable secure communication between the two endpoints, establishing the framework for building the secure tunnel that encapsulates data traffic.

Other choices represent technologies that do not serve the same purpose. AES is a symmetric encryption algorithm, commonly used for encrypting the data within the tunnel but not for establishing the tunnel itself. TKIP is an older encryption protocol used in wireless networks and does not relate to VPN tunnels. The 802.1Q is a networking standard for virtual LANs (VLANs) and plays no role in IPSec or VPN technology.