Which of the following probes can create excessive overhead and should only be used in rare situations?

NetFlow is a network protocol designed for collecting IP traffic information and monitoring network traffic patterns. It operates by capturing flow records from routers and switches, allowing administrators to analyze network performance and usage statistics. However, using NetFlow excessively, especially in large networks, can create significant overhead.

The overhead generated by NetFlow comes from the additional processing required to capture, store, and analyze flow data. In environments with high traffic volumes, the NetFlow export can generate large amounts of data that need to be sent to the collector. This can stress the network and degrade performance, especially if multiple devices are configured to export flows simultaneously.

Due to this potential for excessive overhead, administrators are advised to use NetFlow judiciously and only when necessary for monitoring or troubleshooting purposes. In most scenarios, other methods of monitoring network performance might be preferred to minimize the impact on network resources.

On the other hand, the other choices, such as DNS, RADIUS, and DHCP helper, generally do not create the same level of overhead as NetFlow when configured properly and are often used more routinely in network environments without significant adverse effects.