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Span Port


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Cisco Catalyst Switches have a functionality that allows you to span a port for Packet Analysis.  See this article for more info:


Does any one know if there is a Linux application that can duplicate this technology? My goal is to have an in-line device with with two network interfaces that can do port spanning.

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You could do it with a computer that has three network cards.

Bridge two the network cards so they are seamlessly, then route all in bound traffic on the two ports to the third network card, all inbound traffic on the third card should have no route ('null routed').

A WRT can't do this as it only has two network adapters. You need some thing with three network adapters. Perhaps one of those NAS devices that you can install Linux on, plug two additional NIC's in to to it's USB ports.

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  • 5 months later...
I know this may be reaching into the past but, a hub is what you are looking for. A hub is often used because switches used to only have one span port.

A hub isn't quite right. A hub would be noticeable if you where trying to be stealthy about it (for what ever reason).

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