What message is displayed when a packet is dropped due to a reverse path forwarding check failure?

When a packet is dropped due to a failure in the reverse path forwarding check, the specific message displayed is "Reverse path check fail, drop." This message informs you that the packet could not be validated against the network's routing table for its return path. The reverse path forwarding (RPF) check is an important mechanism used in network devices to prevent certain types of network attacks, such as IP spoofing. If the device cannot verify that the source IP address of an incoming packet is reachable via the routing table's best path, it will discard the packet. This helps ensure that only legitimate traffic is processed and helps maintain the integrity of routing paths in the network.

Other options, while they might seem plausible, do not accurately capture the standard terminology used in security appliances when an RPF check fails. They may use different phrasing or terminology that does not align with the specific diagnostics typically provided by networking hardware.