Which security feature can protect DMVPN tunnels?

IPSec (IP Security) is the standard protocol suite used to provide confidentiality, integrity, and authentication for DMVPN tunnels, encrypting the data payload and authenticating the peers to secure the VPN communication. DMVPN relies on IPSec to secure the Generic Routing Encapsulation (GRE) tunnels, making it a robust solution for secure site-to-site connectivity.

TACACS+ is an AAA protocol used for device management and access control, not for securing data plane traffic within VPN tunnels.

RTBH (Remotely Triggered Black Hole) routing is a technique for mitigating Denial of Service (DoS) attacks, not for securing VPN tunnels.

RADIUS is an AAA protocol used for centralized authentication, authorization, and accounting, not for encrypting or securing the data path of a VPN tunnel.