Reactive mode, on the other hand, is when the network is configured automatically in response to current network conditions. This mode is primarily used for laptop computers and notebook personal computers (PCs) and in situations where network conditions might change.
In reactive mode, a network daemon (nwamd) monitors the state of the system's network interfaces. Whenever network conditions change, the network daemon adjusts the network configuration dynamically. For example, a notebook PC might be physically attached to the corporate network, or it might not be physically attached. When physically attached, you most likely would disable the notebook's wireless interface. Also, it is most often desirable to have the wireless interface automatically enabled when the Ethernet cable is detached from the notebook. In addition, you might want the system to automatically adjust IP Filter settings when switching to a wireless network. The network daemon can automatically perform these types of dynamic configuration changes for you if you are in the reactive mode. Conversely, these types of changes require manual reconfiguration steps if you are in the fixed mode.