Refer to the exhibit.

A GRE tunnel between R1 and R2 has been configured over an Internet connection. As soon as
traffic is sent over the tunnel, high CPU utilization is observed on R1. Reducing the traffic shows a
reduction in CPU utilization. What could be a possible cause for the high CPU utilization?

A.
The BGP process is processing the complete Internet routing table.

B.
An MTU issue causes GRE packets to be fragmented.

C.
A GRE-based DDoS attack is overloading the router control plane.

D.
All GRE packets are always process switched.