You want to ensure traffic is routed through a GRE tunnel. In this scenario, which two statements will satisfy this requirement? (Choose two.)

To successfully route traffic through a Generic Routing Encapsulation (GRE) tunnel, two fundamental routing requirements must be met. First, the tunnel endpoints must possess a route that directs the payload traffic into the tunnel interface (e.g., a static or dynamic route pointing to the gr- interface). Without this, the router will not know which traffic should be encapsulated. Second, because GRE encapsulates the original packet within a new IP header, all intermediary routers between the source and destination endpoints must have a valid route to the outer IP addresses (the tunnel endpoints). The intermediary devices route the encapsulated packets based solely on this outer IP header, meaning they do not need routes to the internal payload destinations, only to the endpoints themselves.

C. Keepalives must be used on stateless tunneling protocols: Keepalives are optional mechanisms used to monitor tunnel interface status and detect failures; they are not a mandatory requirement for routing traffic through a GRE tunnel.

D. BFD must be used on the stateless tunneling protocols: Bidirectional Forwarding Detection (BFD) is an optional protocol used for rapid fault detection. It is not strictly required to establish or route traffic through a stateless GRE tunnel.

1. Juniper Networks. (n.d.). Junos OS Services Interfaces Library for Routing Devices. Section: "Understanding GRE Tunnels". This document specifies that for a GRE tunnel to function, the routing table must contain a route to the tunnel destination (intermediary routing) and a route directing the desired payload traffic into the tunnel interface.

2. Farinacci, D., Li, T., Hanks, S., Meyer, D., & Traina, P. (2000). Generic Routing Encapsulation (GRE) (RFC 2784). Internet Engineering Task Force (IETF). Section 2: "Structure of a GRE Encapsulated Packet". (https://doi.org/10.17487/RFC2784). This RFC details the separation of the delivery protocol (requiring intermediary routing to endpoints) and the payload protocol (requiring endpoint routing into the tunnel).