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Re: 2 nics, 1 network, puzzle?



    "Shawn" == Shawn Yarbrough <shawn@nailstorm.com> writes:

    Shawn> What everybody seems to be telling me is that because IP is
    Shawn> routable, ARP replies are also routable, and the kernel is
    Shawn> free to mix and match IP addresses with Ethernet interfaces
    Shawn> however it likes according to it's IP routing conventions.
    Shawn> I don't agree with this.

Well.... ;-)

    Shawn> ARP is the glue between a specific Ethernet address and a
    Shawn> specific IP address.  When I configured my network, I
    Shawn> explicitly bound two IP addresses to two Ethernet
    Shawn> addresses.  The kernel SHOULD NOT be free to decide that I
    Shawn> was wrong, randomly binding one IP address to the other
    Shawn> Ethernet address after the fact.

If I remember correctly (not having the RFC in front of me) you don't
bind MAC addresses to IP in any sense at all. In fact, when you
configure the interface you do no IP to ARP binding. By definition, IP
to ARP is not bound, that's why you have a discovery protocol with an
ARP *cache*. Remember, IP was not designed to run exclusively on
ethernet!!!  There's a reason it's called the "Internet" protocol, and
that ARP is a fairly high RFC number (in the 800's I think....)

Also, as Jason Healy points out in a different message, you also bound
*networks* to each interface and so on....

I respectfully submit that your expectation is simply the result of
mistaking the common case (ethernet) for the general (IP as a network
layer). 

Cheers!
Shyamal


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