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    SubjectRe: BUG: 2 NICs on same network
    Vincent Guffens wrote:

    > ok, I see, so both interfaces are replying to the arp request but this time, the first interface to reply, eth0, will have its
    > arp reply filtered by the arp_filter as ip_route_output will indicate eth1 as the outgoing interface for a packet that has its
    > source set to the ip to resolve, which has a source route policy entry to point to eth1, is it ?

    Correct. Both NICs receive the arp request, only one of them actually sends a
    reply.

    > But then, by curiosity, is there some reasons why two different interfaces shouldn't be in the same subnet ? I was in this
    > impression having configured some cisco routers which don't even accept this configuration. Is it possible on other network
    > devices ? Is there any theoretical justification ?

    I don't think there are any theoretical objections. I'm pretty sure windows
    will let you do it, but they don't give you nearly as much control over the
    routing.

    Without source routing or arp filter, traffic to any of the interfaces on the
    same subnet can go through any of the interfaces on that subnet--whichever arp
    reply gets there last is the winner. This can be useful for quasi-redundant
    type communications, but causes big problems if you're trying to monitor the
    state of your network communications paths. This is where the more strict
    behaviour becomes useful.

    Chris


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    Chris Friesen | MailStop: 043/33/F10
    Nortel Networks | work: (613) 765-0557
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