bridge and tcpdump - Networking

This is a discussion on bridge and tcpdump - Networking ; i have a problem with a bridge i can create a bridge, and it work fine i have a bridge with 3 pc and they can ping any other but when i run 'tcpdump -n' in for example pc1 and ...

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Thread: bridge and tcpdump

  1. bridge and tcpdump

    i have a problem with a bridge

    i can create a bridge, and it work fine
    i have a bridge with 3 pc and they can ping any other

    but when i run 'tcpdump -n' in for example pc1 and do ping from pc2 to pc3
    tcpdump don't capture anithing

    why?

    sorry for my bad english

    --
    Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    sul http://www.iltermitano.it/)

    A computer is like an air conditioner,
    it stops working when you open Windows.
    Registered Linux user #457776

  2. Re: bridge and tcpdump

    On Sep 17, 8:50*am, RicK_Murphy

    wrote:
    > i have a problem with a bridge
    >
    > i can create a bridge, and it work fine
    > i have a bridge with 3 pc and they can ping any other
    >
    > but when i run 'tcpdump -n' in for example pc1 and do ping from pc2 to pc3
    > tcpdump don't capture anithing
    >
    > why?


    Because the bridge knew that the packet didn't have to go that way.

    DS

  3. Re: bridge and tcpdump

    RicK_Murphy writes:

    > but when i run 'tcpdump -n' in for example pc1 and do ping from pc2 to pc3
    > tcpdump don't capture anithing


    It must be a switch and not a hub.

    A hub is dumb. Everry port sees the same thing. A switch will only
    have traffic on the ports that uses it. So if you have three ports: 1,
    2, and 3

    when PC2 sends to PC3, PC1 will not see it.


    You need a switch that can do port mirroring, like the Dell
    PowerCOnnect 2700 series.

    http://www.dell.com/content/products...d&cs=04&~ck=bt


    Configure one of the ports to mirror all of the data from the other ports, and connect your sniffer to that machine.


    The 2708 (8-port switch) can run port mirroring on up to 4 ports.

    Or else run the sniffer on one of the end points.....
    This may affect your measurements.

  4. Re: bridge and tcpdump

    RicK_Murphy wrote:


    > but when i run 'tcpdump -n' in for example pc1 and do ping from pc2 to pc3
    > tcpdump don't capture anithing


    when, whit my linux I do this one:

    brctl setageing 0

    I obtain a bridge, it works lika a hub and not like a switch

    --
    Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    sul http://www.iltermitano.it/)

    A computer is like an air conditioner,
    it stops working when you open Windows.
    Registered Linux user #457776

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