Multiple leases

Simon Hobson dhcp at
Fri Jun 9 18:58:56 UTC 2006

>  >  > If the lease is FREE or BACKUP (does the client release its lease?),
>>>   then the behaviour is more reasonable - both servers must answer, and
>>>   they can only offer leases in one of those two states.
>>I would guess that they don't as there a very few RELEASE messages in
>>the logs, it would appear that MacOS X doesn't do a release when a NIC
>>is shutdown.
>I can't say what happens when you shutdown an interface, or put a
>machine to sleep (and I don't have enough working Macs to hand to
>test it). I do know that when you shut down the OS it releases it's
>lease - it would be logical to handle other ifdown events the same

I've now checked (Powerbook G4 running OS X 10.4), and it appears that :

On going to sleep, it does nothing.
On waking from sleep, it does Request-Ack.

Reboot and Shutdown/Startup are the same*.

On unplugging a network cable, it can't do anything !
On plugging it back in, it does Request-Ack.

Turning off Airport (as opposed to deselecting it as an active 
interface in Network prefs) appears to have the same effect as 
unplugging an ethernet cable - ie it doesn't do a release.

On shutting down an interface (via Network prefs), it does Release.
On turning it back on, it does Discover-Offer-Request-Ack.

* This is a change from the behavior I remember observing in the 
pre-OS X days. Back then, I know that they released their leases on 
shutdown - which was 'interesting' on the morning I killed the dhcp 
server !

So, normal operations (sleep/wake, reboot, shutdown/startup) do not 
result in a release, this only seems to happen if you go into Network 
prefs and disable the interface from the list of active interfaces.


More information about the dhcp-users mailing list