Which statement regarding the benefits of using GRE instead of IP-IP tunneling is true?

Using Generic Routing Encapsulation (GRE) offers several advantages over IP-in-IP tunneling, and one of the key benefits is that GRE supports both IP traffic and non-IP traffic. GRE encapsulates packets in a standardized method that allows not only IP packets but also other types of protocol data units (PDUs), such as AppleTalk, IPX, and others. This versatility makes GRE an attractive option for network engineers who need to encapsulate varied types of network traffic across a tunnel.

In contrast, IP-in-IP tunneling is limited to only IP packets. Therefore, organizations that require the ability to encapsulate a wide range of protocol traffic will find GRE to be the more suitable choice.

While other options mentioned have their own merits, such as encryption and authentication, they are not inherent features of GRE itself. GRE does not natively support encryption or authentication, although these can be added using other protocols or technologies, such as IPsec. Thus, the distinct capability of GRE to handle both IP and non-IP traffic is what truly sets it apart in this context.