In the Environment of GRE Configuration, Which of the Following

In the environment of GRE configuration, which of the following statements are true? (Choose three.)

A) In order to make the ends of the tunnel forward data packets normally, the devices of both ends are configured routing which through the Tunnel interface
B) If both ends enable the configuration of keyword verification, the keyword must be the same
C) When the local device send data packets, by identifying the protocol field value of IP header for GRE to determine whether send the data packet to GRE module for processing
D) When the opposite end receives data packets, by identifying the protocol field value of IP header for GRE to determine whether send the data packet to GRE module for processing