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    SubjectARP (mis)behavior
    I'm doing some work with network drivers, and have run across some strange
    ARP behavior in testing that seems to stem from the IPv4 stack. ARP replies
    seem to ignore any mapping between devices and IP addresses, so that as long
    as an IP is assigned to one interface all the interfaces on a given machine
    will respond to the ARP request.

    As a simple example, if a server has two Ethernet cards connected to the
    same network configured as and From a client machine,
    say, pinging both server addresses seems to work, but looking at
    the ARP cache reveals that often one interface has responded to both ARP
    requests. More interesting, if one interface is brought down the other will
    continue to respond to ARP requests and any other network traffic for the
    downed adapters IP address.

    In a situation where multiple adapters are on the same network segment, the
    Linux IPv4 stack behaves as if a many-to-many mapping of a pool of IP
    addresses onto a pool of network adapters exists.

    While this does provide some basic fail-over capabilities, I can't imagine
    that this is expected or desired behavior. If this is the intended
    behavior, I'd be interested in hearing why ARP was implemented this way. If
    not, I may have time to try and change this and submit a patch.

    (note: I'm having trouble sending to the list from my Intel account, please
    ignore the fact that I'm sending from my account)

    Chris Leech
    Intel Network Communications Group

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      Last update: 2005-03-22 13:53    [W:0.020 / U:65.588 seconds]
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