Spanning a port disables remote access from my desktop

Posted on 2006-04-12
Last Modified: 2013-12-06
Greetings Experts,

I have an IDS system (Fedora core 4) that is plugged into a switch (on port 3) that is configured to copy traffic on ports 1 and 2.  Before this configuration I was able to ssh to the IDS box and ping it from my desktop.  However, after I set up the configuration for port spanning I am not able to connect.  Can someone give me an idea of what could be the problem?  Your thoughts, ideas or comments most certainly appreciated.

Question by:Ironman88
    LVL 15

    Accepted Solution

    Depends on the switch but the span will usually stop incoming packets on the destination port because bridging loops can occur. While you could probably allow incoming to be able to access the box, best solution is to use two interfaces connected to a switch port each. One is for control and access while the other monitors the mirrored ports.
    LVL 1

    Expert Comment

    Frabble is right,

    if you SPAN a port, the TX pair on that port is effectivly disabled - thus preventing your IDS from participating on the network
    You need to add a second nic to your FC box, and connect that to your network so you can ssh.

    took me days to figure that one out :)

    Author Comment

    Thank you that was just what the doctor ordered.  I added the second nic and life is much better.


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