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Using A Span Port - Cisco AMP8050 Hardware Installation

Firepower 8000 series
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Chapter 6
Deploying Firepower Managed Devices

Using a Span Port

Many network switches include a span port that mirrors traffic from one or more ports. By connecting
an interface set to the span port, you can monitor the combined traffic from all ports, generally both
incoming and outgoing. If you already have a switch that includes this feature on your network, in the
proper location, then you can deploy the detection on multiple segments with little extra equipment cost
beyond the cost of the managed device. In high-traffic networks, this solution has its limitations. If the
span port can handle 200Mbps and each of three mirrored ports can handle up to 100Mbps, then the span
port is likely to become oversubscribed and drop packets, lowering the effectiveness of the managed
Using a Network Tap
Network taps allow you to passively monitor traffic without interrupting the network flow or changing
the network topology. Taps are readily available for different bandwidths and allow you to analyze both
incoming and outgoing packets on a network segment. Because you can monitor only a single network
segment with most taps, they are not a good solution if you want to monitor the traffic on two of the eight
ports on a switch. Instead, you would install the tap between the router and the switch and access the full
IP stream to the switch.
By design, network taps divide incoming and outgoing traffic into two different streams over two
different cables. Managed devices offer multiple sensing interface options that recombine the two sides
of the conversation so that the entire traffic stream is evaluated by the decoders, the preprocessors, and
the detection engine.
Cabling Inline Deployments on Copper Interfaces
If you deploy your device inline on your network and you want to use your device's bypass capabilities
to maintain network connectivity if the device fails, you must pay special attention to how you cable the
If you deploy a device with fiber bypass capable interfaces, there are no special cabling issues beyond
ensuring that the connections are securely fastened and the cables are not kinked. However, if you are
deploying devices with copper rather than fiber network interfaces, then you must be aware of the device
model that you are using, because different device models use different network cards. Note that some
8000 Series NetMods do not allow bypass configuration.
The network interface cards (NICs) in the device support a feature called Auto-Medium Dependent
Interface Crossover (Auto-MDI-X), which allows network interfaces to configure automatically whether
you use a straight-through or crossover Ethernet cable to connect to another network device. Firepower
devices bypass as crossover connections.
Wire the device as would normally be done without a device deployed. The link should work with power
to the device removed. In most cases you should use two straight-through cables to connect the device
to the two endpoints.
Connecting Devices to Your Network
Firepower 8000 Series Hardware Installation Guide


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