Cisco Cisco Firepower Management Center 4000

If a secondary device fails, the primary device continues to sense traffic, generate alerts, and send traffic 
to all secondary devices. On failed secondary devices, traffic is dropped. A health alert is generated 
indicating loss of link.

You can use a device stack as you would a single device in your deployment, with a few exceptions. If 
you have clustered devices, you cannot stack a device cluster or a device in a clustered pair. See 

 for more information. You also cannot configure NAT on a device stack.

If you use eStreamer to stream event data from stacked devices to an external client application, collect 
the data from each device and ensure that you configure each device identically. The eStreamer settings 
are not automatically synchronized between stacked devices.

See the following sections for more information:

Any

3D8140, 3D8200 family, 3D8300 family, 3D9900

You can increase the amount of traffic inspected on a network segment by stacking two fiber-based 
3D9900s, two 3D8140 devices, up to four 3D8250s, a 3D8260, a 3D8270, a 3D8290, up to four 3D8350s, 
a 3D8360, a 3D8370, or a 3D8390 and using their combined resources in a single, shared, configuration. 
Before you begin, you must:

decide which unit will be the primary device

cable the units properly before designating the primary/secondary relationship. For information 
about cabling, see the FireSIGHT System Installation Guide.

If you have clustered devices, you cannot stack a device cluster or a device in a clustered pair. However, 
you can cluster a device stack. See 

 for more information.

After you establish a device stack, the system treats the devices as a single device on the Device 
Management page. Device stacks display the stack icon (

) in the appliance list.

Removing registration of a device stack from a Defense Center also removes registration from both 
devices. You delete stacked devices from the Defense Center as you would a single managed device; you 
can then register the stack on another Defense Center. You only need to register one of the stacked 
devices on the new Defense Center for the entire stack to appear. See 

 and 

 for more information.

After you establish the device stack, you cannot change which devices are primary or secondary unless 
you break and reestablish the stack. However, you can:

add secondary devices to an existing stack of two or three 3D8250s, a 3D8260, or a 3D8270 up to 
the limit of four 3D8250s in a stack