What situation creates excessive traffic across a network, leading to a denial of service attack?

In the context of a denial of service attack, the situation that creates excessive traffic across a network is a switching loop. A switching loop occurs when there are multiple paths in a network that lead to the same destination, causing data packets to circulate endlessly between switches. This creates significant broadcast traffic as the switches continuously forward packets to one another rather than reaching their intended destinations.

What makes switching loops particularly problematic is that they can cause multiple issues, such as high CPU utilization on switches and, eventually, network congestion that leads to a denial of service. When the network becomes overwhelmed with this excessive traffic, legitimate users may experience slowdowns or complete unavailability of network services.

Other options, such as broadcast storms, network flooding, and network congestion, do indicate scenarios where traffic may become excessive, but they are often more specific manifestations or results of conditions like switching loops, rather than the overarching situation that characterizes a denial of service attack caused by a malfunctioning network design. Therefore, identifying a switching loop as the source of excessive traffic is critical in understanding how these attacks can manifest.