dhcp-users Digest, Vol 5, Issue 58

[Marc Perea]

Staffan,
we actually ran into this recently ourselves when testing out a Vista client, and packet captures provided insight. From our testing, it seems that Vista does a "gratuitous arp" for the IP it was given, meaning that it asks anyone on the L2 attached network if they belong to the IP handed back via DHCP to Vista. In our case, this was a problem because of a router config that responded to that arp - in short the router said, "Sure, that IP is mine and here's my MAC", even though the router was just proxying and trying to say, "I know how to get to that IP, so I'll just pretend that I'm that IP from your perspective" - i.e. you can get to that IP through my MAC. Anyhow, iirc Vista doesn't actually use ping, but instead arps to scan for IP usage on the network. Also, Vista would NAK the server's ACK message for the lease, and we fixed this by reconfiguring a setting on the router. Hope that helps...

--Marc

>
>Message: 6
>Date: Tue, 17 Mar 2009 12:57:56 +0100
>From: <Staffan.Ungsgard at teliasonera.com>
>Subject: RE: use og ping-check
>To: <dhcp-users at lists.isc.org>
>Message-ID:
>	<E21F210743B900428148A444E75E462002F4F914 at SEHAN015MB.tcad.telia.se>
>Content-Type: text/plain; charset="iso-8859-1"
>Does the ISC Dhcp server Windows Vista work together regarding to "ping" ?
>
>This is a snippet from Microsoft regarding Windows Vista and ping: 
>
>"After you assign or change an IP address on a Windows Vista-based computer, the system searches the network for a computer that is already using this IP address. >If the search reveals no computer that is already using this IP address, the IP address is officially assigned to the Windows Vista-based computer. The problem that is >>described in the "Symptoms" section occurs if another computer sends a ping message to the new IP address before the system finishes the search process. The >.system was not designed to be pinged while it is searching for a new IP address. " 

>Full info here: http://support.microsoft.com/kb/948363 

>Can the DHCP-server ping makes Vista nack the lease because it thinks someone else has the address ?