One IP for several Interfaces

John Wobus jw354 at
Fri Feb 20 22:59:20 UTC 2015

On Feb 20, 2015, at 3:58 PM, Simon Hobson wrote:
> Алексей Прокопчук <alexpro at> wrote:
>>> I don't know whether MacOS detects IP conflict or not.
> It does if it's offered/configured with an address which it detects  
> in use by *another* system on the network. It doesn't complain about  
> itself.

But if it's connected twice to the same broadcast
domain, would it figure out that a test arp from
another MAC address is itself?

A host that doesn't bother to arp-check might "work".
If the router's ARP entry for the host flaps, all traffic
theoretically still goes to the host.  Not really
a clean setup, but it might work and perhaps
not even slow you down too much.  Actual flaps
would be triggered any time the host
chose to send a packet out its other interface.

If dhcpd is arp-checking, it should complain irrespective
of the client system.  Reckless clients that forgo an arp
check perhaps could appear to work fine.  Then another
client that conscientiously does the check is the one
that looks strange.

John Wobus
Cornell University IT

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