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SubjectRe: Linux 2.2 - BSD/OS 4.1 ARP incompatibility
On Sat, Sep 02, 2000 at 12:28:00PM +1100, David Luyer wrote:
>
> I'm seeing a problem between Linux 2.2 and BSD/OS 4.1 in the situation on one
> of our backbones.
>
> We have a number of Linux hosts on this backbone with a primary address in
> the network a.b.c.0/24 and a secondary address in the network d.e.f.0/24.
>
> We also have some BSD/OS 4.1 machines in this network with addresses in
> d.e.f.0/24 only.
>
> Now when the Linux box a.b.c.1 (with secondary address d.e.f.1) wants to
> talk to the BSD/OS system d.e.f.2 it does
>
> a.b.c.1 arp who-has d.e.f.2
>
> Which d.e.f.2 promptly ignores, presumably because the IP stack in BSD/OS
> throws it away at a low level, or possibly simply because BSD/OS has no
> idea where to send the ARP response.
>
> The end result is that a.b.c.1 can't talk to d.e.f.2 because it does an ARP
> from the wrong IP address and doesn't get a response.
>
> Is this already fixed in 2.4 or it is something which needs investigation
> and a patch?
>
> According to the standards, who is in the wrong? To me it looks like Linux
> is the misbehaved OS in this case.

Strictly it is your routing which is wrong, because you're giving different
routing information to BSDI and Linux.

To work around it you can set an explicit source address on the outgoing
routes using ip route replace d.e.f/24 src a.b.c.NUM dev DEV

-Andi
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