DHCP Reservations

[poma]

On 03.02.2015 08:01, Tim wrote:
> On Mon, 2015-02-02 at 11:20 -1000, Jim Lewis wrote:
>> Quick question about DHCP reservations: I have laptops with both wired
>> and wireless NICs, is it okay to have the router assign the same IP to
>> both interface?
> 
> I seem to recall being able to do that, with the DHCP server on my
> Fedora Core 4 installation (having two separate MAC matching clauses
> that applied the same IP).  Other servers may try to prevent you doing
> that, as it can be problematic.
> 
> The client behaviour could be a bit wierd, especially if the client
> doesn't completely bring down the interface that previously had the same
> IP.  On some clients, plugging in a cable doesn't disable or override
> the wireless.  You'd have to manually do so.
> 
> And lease expiry time wasn't an issue, that would only apply if I was
> hoping for a dynamically supplied IP to be re-supplied.  My
> configuration was fixed IPs doled out by the DHCP server.  So if your
> MAC matched, you were assigned that IP, as long as something else didn't
> prevent it.
> 

The combination of the same IP address on two different network interfaces is prohibited for obvious reasons. At least via the WebUI.
But no one defends leave one network interface on the router DHCP static leas, and make local static profile with the same IP with other network interface, making sure that both interfaces are not simultaneously in operation.
However if someone decides to do the same on the LAN, there goes a trouble.
Also not to be excluded, in the absence of a morning dose of caffeine, the one that set the same address at the two interfaces can confuse imself.
All in all it's just a call to the circus.