This is a network-based IDS, supplied as an appliance. There are four versions of the NID-300 series - the difference being in the number and speed of the Ethernet interfaces. The top-of-the-range model has two 10/100Mbit and two gigabit network interfaces. One of these interfaces is always reserved for management, but the remainder can be used for monitoring. In this way, a single NID-300 can monitor load-balanced or failover WAN connections. By separating the management and monitoring interfaces, NID-300 can operate in stealth mode, as the monitoring interface does not respond to any network traffic or requests from any service on the monitored network.