Fail-open versus fail-closed

Sensor ports deployed in In-line Mode have the option of failing open or closed. Similar in terminology to firewall operation, ports failing open allow traffic to continue to flow. Thus, even if the ports fail, your Sensor does not become a bottleneck; however, monitoring ceases which may allow bad traffic to impact systems in your network. When ports are configured to fail closed, the Sensor does not allow traffic to continue to flow, thus the failed ports become a bottleneck, stopping all traffic at the Sensor.