Reply #63: From a very well-informed source

[Carolab]

I got this reply:

This is an error message you would see on a DHCP server, indicating that not
only was the machine networked, but it received requests from another computer
for an address out of the DHCP scope or that may have been already assigned.

More info:

http://support.microsoft.com/kb/163055/EN-US/ and
http://www.eventid.net/display.asp?eventid=1011&eventno=451&source=DhcpServer&phase=1

Basically, this indicates that the machine was both connected to a network AND
received requests for an IP address from another computer, which this machine
was apparently supposed to provide.

As an aside, you usually see DHCP NACKs with multi-homed servers, meaning that
usually this happens in servers with more than one network connection (could be
a network card and modem, 2 network cards, network card and wireless card,
etc).

If you Google DHCP NACK you'll get more info - basically this is how it works:

client > dhcp discover
server > responds with dhcp offer
client > sends dhcp request
server > responds with DHCP ACK (acknowledge) or NACK (not acknowledge, which
retracts the offer)

This is the last step in the DHCP addressing process, and a NACK should result
in re-initialization of the client, starting the process over. That is a
little oversimplified - for more detailed info please check out RFC 1541 and
2131, at http://info.internet.isi.edu/