Refer to the exhibit.

Refer to the exhibit. Routers R1 and R2 are connected over the internet, with the connection passing over four different autonomous systems. The company must mitigate potential DDoS attacks and protect the CPUs of the routers. A network engineer must secure all external connections on edge router R1 based on RFC 5082. R2 has already been secured. Which task should the engineer perform on R1 to achieve the goal?