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Hi all, this is my first post on this forum and I hope to solve my problem with your hints. I need to have the configuration showed on the attached ...
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  1. #1
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    Cable disconnection Eth0 and Eth1 behaviour


    Hi all,

    this is my first post on this forum and I hope to solve my problem with your hints.
    I need to have the configuration showed on the attached file. I have two machines, one PC (ubuntu 9.10 ) and one embedded CPU with a tailored linux version starting from 2.4.31 linux kernel with Busybox running on PPC architecture.
    PC address is 192.168.30.70.
    On CPU board I have two ethernet interfaces with addresses :
    eth0 192.168.30.30 netmask 255.255.255.0
    eth1 192.168.30.40 netmask 255.255.255.0
    PC sends messages alternatively to 192.168.30.40 and to 192.168.30.30 .Between two machines there is an ethernet switch to allow messages flowing.

    I use ping (from two shells on PC I ping the two addresses on CPU) to simulate messages from PC to CPU and I see this behaviour:
    Starting from a situation in which CPU responds to the pings I try to disconnect cable connected to eth0 on CPU. I cannot see any interruption on ping reply on the eth0 port. If i reconnect the cable on eth0 and I disconnect cable on eth1 there are no reply to the two pings (neither from eth0 nor from eth1). It seems that all data flows on one cable just because the addresses are on the same subnet. Is this right?
    If this is the right behaviour how can i separate data from PC to CPU in order to force packets to flow on two cables and avoid this sort of internal routing beetween eth0 and eth1?

    TIA,

    Alberto
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  2. #2
    Linux Guru Lazydog's Avatar
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    You should never have 2 nics on the same network unless you are bundling the interfaces to work as one. What you are seeing is normal and it could be that the switch has shut down one of the interfaces as it sees a routing loop.

    Regards
    Robert

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  3. #3
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    Thanks for your answer.
    Now moving the problem on the switch my question is: is it possible (when eth0 or eth1 is disconnected) to re-route data to the connected cable? I think it's a question of recalculate new paths to the CPU...

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  5. #4
    Linux Guru Lazydog's Avatar
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    I have answered your question. Look into bonding the interfaces.

    Regards
    Robert

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