Refer to the exhibit. An engineer troubleshoots connectivity issues with an application. Testing is performed from the server gateway, and traffic with the DF bit set is dropped along the path after i

When the DF (Don't Fragment) bit is set and a packet exceeds an intermediate link's MTU, the router must drop the packet and send an ICMP 'Packet Too Big' message back to the sender. If these ICMP messages are blocked, for instance by an ACL, the sender cannot learn the correct Path MTU and will continue to send oversized packets that get dropped, indicating PMTUD failure.

While high CPU load can cause drops, the specific interaction with the DF bit and packet size, and the resolution by removing the DF bit, strongly points to an MTU/PMTUD issue rather than general CPU overload.

Setting the DF bit is a common practice for many applications to leverage PMTUD and avoid IP fragmentation, which can degrade performance; the problem lies not in setting the DF bit, but in the failure of PMTUD when it is set.

Control Plane Policing (CoPP) protects a router's CPU from excessive traffic destined *to* the router itself (e.g., management or routing protocols) and typically does not drop forwarded data plane traffic based on the DF bit or MTU in this manner.