Setting up simple SPAN port, same interface for computer / Linux?

Posted on 2007-10-01
Last Modified: 2012-06-21
I'm working with a colo, so I have limited "access" into the network port itself. All I want to do, is set a SPAN port for a VLAN on a Cisco 2900, then have a Linux box monitor that port, and OF COURSE still be accessible from here at our location. They already moved the port and made it a SPAN port, but NOW I can't get to the computer. I'm not sure what's the deal. It's like they're setting up out-of-band SPAN somehow? I just want in-band same traffic to get to the computer as the SPAN. Is that OK? Does that work? Do I NEED another network port? If so, do I set anything on the SPAN port or just leave it without IP or anything?

So... I'm asking about setting up a SPAN port for a computer with one network interface basically.
Question by:ldorazio
    1 Comment
    LVL 11

    Accepted Solution

    You cannot communicate over monitoring port, it becomes uni-directional and receives traffic only. It's made this way to avoid confusion when communications with your system will be mixed up with the port you are trying to monitor and to avoid some sort of traffic loops if your system will try to send anything toward monitored port it will be reflected at monitoring port. So for your Linux you need a separate interface for a SPAN port.

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