Re: 2 nics, 1 network, puzzle?
On 26 Mar 2002 21:43:24 -0600
Shyamal Prasad <shyamal.prasad@sbcglobal.net> wrote:
> I don't think there is anything wrong or strange. The system knows
> that there are two routes to the network, and it is free to use either
> one as it pleases.
What everybody seems to be telling me is that because IP is routable, ARP
replies are also routable, and the kernel is free to mix and match IP
addresses with Ethernet interfaces however it likes according to it's IP
routing conventions. I don't agree with this.
ARP is the glue between a specific Ethernet address and a specific IP
address. When I configured my network, I explicitly bound two IP
addresses to two Ethernet addresses. The kernel SHOULD NOT be free to
decide that I was wrong, randomly binding one IP address to the other
Ethernet address after the fact.
But that's what it clearly seems to be doing:
1) the ARP request for IP address .131 reaches the kernel
2) the kernel notices that IP address .131 is bound to Ethernet address
eth1, meaning that the kernel must now generate an ARP reply
3) the kernel decides to ignore the information it already has (that .131
equals eth1) and instead generates an ARP reply falsely advertising that
.131 equals eth0
4) the ARP reply goes out on eth0
This is not an IP routing situation. IP .131 does not equal eth0. I
don't think it can do #3. Yet it seems to be doing just that. I would be
OK if it was only doing steps 1, 2, and 4. Step 4 would seem a little
weird for an eth1 ARP reply but it wouldn't actually hurt anything IMVHO.
But step 3 is effectively rebinding my IP to Ethernet assignments without
my permission.
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