Refer to the exhibit. If R1 is connected upstream to R2 and R3 at different ISPs as shown, what action must be taken to prevent Unicast Reverse Path Forwarding (uRPF) from dropping asymmetric traffic?
A. Configure Unicast RPF Loose Mode on R2 and R3 only.
B. Configure Unicast RPF Loose Mode on R1 only.
C. Configure Unicast RPF Strict Mode on R1 only.
D. Configure Unicast RPF Strict Mode on R1,R2 and R3.
E. Configure Unicast RPF Strict Mode on R2 and R3 only.
