I need to setup two computers with the same ip in the same subnet

Discussion in 'Linux Networking' started by zido, Jul 10, 2003.

  1. zido

    zido Guest

    This is the problem:

    I've got two computers in the same subnet. Computer A with two
    network cards and computer B with just one. I need to install a
    software licensed to an ip address. This ip address is used by one
    computer (Computer A).

    Computer A/Windows: eth0
    Computer B/Linux: eth0
    ---------------------------- netfilter/iptables

    If I setup iptables in order to hide the B/eth1 from the rest of
    the subnet, all the services are unreachable. The problem is that I
    need to drop all the arp requests too. If I configure eth1 with
    'ifconfig eth1 -arp' when any computer in the subnet pings
    the arp table is filled for that address ( with the
    B/eth0's physical address (MAC)... ¿¿??? Why?

    I've got a big mess. Anybody can help me? Thanks.
    zido, Jul 10, 2003
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  2. On Thursday July 10, 2003 at 03:30
    If I follow you correctly, your looking to install software or
    computer:b that you only have a license for on computer:a. Is it just
    me, or is this illegal?
    Johann Koenig, Jul 10, 2003
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  3. zido

    Xyerp Guest

    If you need install a software like this, it sound like you are trying
    to break your EULA. Can't condone this action, sorry.
    Xyerp, Jul 10, 2003
  4. zido

    /dev/rob0 Guest

    Probably so, but it is an interesting situation. :) The best advice of
    course is to eliminate one's dependence upon proprietary software.

    Back to the OP's attempt to violate his software license: I don't think
    you can do it with both in the same subnet. I think you need to put a
    router between them. If the 2 machines with the same IP need to talk to
    one another, this might be done via NAT on the router. The dual-homed
    Linux box cannot use the real IP of the Windows box, because its route
    table will see that as belonging to a local interface.

    BTW IIUC it might not need to have 2 NIC's for this. This sounds like a
    good use for the "dummy" net driver. (The router of course needs 2
    /dev/rob0, Jul 10, 2003
  5. I think what he wants is the card to exist for the software to verify,
    but not be able to communicate with the rest of the network. However,
    I'm not sure how said software verifies itself. Does it just check if
    the address exists, or does it communicate with a verification database?

    I've never heard of verification by IP address before, but I don't deal
    much with proprietary software since I switched to Debian.
    Johann Koenig, Jul 10, 2003
  6. zido

    zido Guest

    you're right. But it's all absolutely legal. The matter is the
    computer B is a test computer and the computer A is a computer with
    users accessing it. Until we do the migration I don't want to change
    anything in computer A (with windows os and application servers with
    ip based configuration), and meanwhile I need a test computer (the
    tests might last months). And after this explanation I wonder if you
    have an answer to my question or if you were bored.

    For other people with the same problem I think there's a clue here :
    zido, Jul 10, 2003
  7. zido

    /dev/rob0 Guest

    Chances are that it won't care about the card per se. If it just uses an
    ifconfig-like means of listing active interfaces, "dummy" would do the
    Yeah, I don't know either. IAC it sounds nasty. :)
    Unfortunately I do have to deal with some here and there. But I'd tell
    my clients not to risk using any unlicensed proprietary software.
    /dev/rob0, Jul 10, 2003
  8. In which case you can contact the vendor and ask for a temporary license
    for your test box. It it's legal and within their terms they will

    Regards, Ian
    Ian Northeast, Jul 10, 2003
  9. zido

    James Knott Guest

    Well, you could buy an additional licence, so you don't have to ask on the
    internet, for help in cheating the software supplier.


    Fundamentalism is fundamentally wrong.

    To reply to this message, replace everything to the left of "@" with
    James Knott, Jul 10, 2003
  10. Yes, I am bored; otherwise, I won't bother with other people's
    This is advanced routing with two nic on same segment.

    You are adding another nic with same IP in addition to that. Two mac
    addresses with same IP is definitely not acceptable. My suggestion is
    to take your test machine off the net while running this apps.
    Edward Lee epl, Jul 11, 2003
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