There are two scenarios where a network engineer needs to exercise his troubleshooting skills. One, when there is network degradation or an incident detected through proactive monitoring of the network as defined in the previous chapter, and two, when a user reports an issue leading to reactive troubleshooting.
It is important for the network engineer to know what normal behavior on the network is. This normal or expected behavior is referred to as the baseline and any unexplained significant deviations from this baseline would be considered abnormal behavior and should be investigated.
