Windows leases through a PC reset

[Glenn Satchell]

>X-Original-To: dhcp-users at webster.isc.org
>Date: Tue, 08 May 2007 11:42:25 -0400
>From: "SCOTT BURGIN" <SBURGIN at salliemae.com>
>To: <dhcp-users at isc.org>
>Subject: Re: Windows leases through a PC reset
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>>>> "SCOTT BURGIN" <SBURGIN at salliemae.com> 5/8/2007 11:04 AM >>>
>Basic question - RFC aside - does anyone have real world knowledge (personally 
conducted testing preferred) of whether a Windows machine will continue to use a 
valid ISC provided lease through a power down/power up sequence when the DHCP 
server(s) are unreachable ?  Does the version of the Windows OS change the 
result ?
>
>It is being challenged in our environment that the Windows machine *wlll not* 
continue to use the still valid lease through a power down/up sequence if it 
can't reach the DHCP server.
>
I just tried this on my test network. Client is Win XP Home SP2. This
should be very easy to re-create on a test network with a single dhcp
server and however many clients you want to try.

These are the snooped packets from the PC as it booted. Note the last
two are from the correct IP address.

OLD-BROADCAST -> BROADCAST    DHCP/BOOTP DHCPREQUEST
OLD-BROADCAST -> BROADCAST    DHCP/BOOTP DHCPREQUEST
OLD-BROADCAST -> BROADCAST    DHCP/BOOTP DHCPREQUEST
dhcp-14-249.uniq.com.au -> BROADCAST    DHCP/BOOTP DHCPINFORM
dhcp-14-249.uniq.com.au -> BROADCAST    DHCP/BOOTP DHCPINFORM

Running ipconfig /all on the PC after booting shows all the settings
are still intact. Note that it is possible to configure dhcp to supply
options that will cause Windows to release the lease when shutdown, but
this is not the default behaviour in any release.

regards,
-glenn