Fail-Open kits minimize the potential risks of in-line Sensor failure on critical network links. You need to purchase these kits separately. Both copper and optical versions of the kit are available for the one-gigabit ports.
Monitoring ports of the Sensors can be fail-close; thus, if the Sensor is deployed in-line fail-close, a hardware failure results in network downtime. Except the built-in RJ-45 ports (G2) which come with built-in fail-open functionality, you use the optional external bypass switch provided in an active or passive fail-open kitsfor the other monitoring ports (G0, G1) to fail-open.
While the Sensor is operating, the active or passive fail-open kits is in-line and routes all traffic directly through the Sensor. When the Sensor fails, the fail-open switch automatically shifts to a bypass state; in-line traffic continues to flow through the network link but is no longer routed through the Sensor. After the Sensor resumes normal operation, the switch returns to the in-line state, enabling in-line monitoring.
G0 supports active and passive fail-open modes using a copper and fiber 1 Gigabit kit with RJ-11 control port and SFP+(10G) Fiber fail-open kit.
G1 supports both active and passive fail-open modes. G1 supports 1G SFP fiber and copper active/passive fail-open kits.
G2 supports internal fail-open and supports active fail-open when connected to an active fail-open kit.
Caution
Sensor outage breaks the link connecting the devices on either side of the Sensor for a brief moment and requires renegotiation of the network link between the two peer devices connected to the Sensor. Depending on the network equipment, this disruption introduced by the renegotiation of the link layer between the two peer devices might range from a couple of seconds to more than a minute with certain vendors' devices.
Caution
A very brief link disruption might also occur when links between the Sensor and each of the peer devices are renegotiated to place the Sensor back in in-line mode. This outage, again, varies depending on the device, and can range from a few seconds to more than a minute. The performance of the switchover from in-line to bypass and vice versa varies depending on the vendor.
You can find the installation and troubleshooting instructions for the kit in the guide that accompanies the kit. For example, for more information on the Optical kits, see the 1 Gigabit Optical Active Fail-Open Bypass Kit Guide.