What two features are benefits of using GRE tunnels with IPsec over using an IPsec tunnel alone in building-to-building site-to-site VPNs? (Choose two.)

GRE over IPsec allows dynamic routing protocols (such as OSPF, EIGRP, BGP) to securely exchange routing updates across the VPN tunnel because GRE provides the necessary generic encapsulation for these protocols, which IPsec alone does not natively support for routing protocol traffic.

IKE keepalives are a feature of IPsec for connection monitoring and are not a benefit unique to combining GRE with IPsec; their specific behavior (unidirectional, 10 seconds) is also not a general comparative benefit.

Using GRE over IPsec actually increases header overhead because both GRE and IPsec headers are added to the original packet, which is more overhead than using IPsec tunnel mode alone.

GRE (Generic Routing Encapsulation) is capable of encapsulating various network layer protocols, including non-IP traffic, enabling them to traverse an IPsec-secured tunnel, whereas IPsec by itself is designed primarily to secure IP packets.

Virtual Tunnel Interface (VTI) is an IPsec feature that simplifies VPN configuration, allowing dynamic routing protocols to run directly over IPsec without an additional GRE tunnel, making it an alternative to GRE over IPsec, not a benefit of it.