DHCP scanning

[Bénoni MARTIN <Benoni.MARTIN () libertis ga>]

Hi list !

I was wondering if there was way to scan a network (a class C) to look for DHCP machines (I know I can ask the DHCP 
server, but I want to know what machines are under DHCP independly, and check after with what the DHCP server claims).

I was thinking about creating such a plugin to report the results in Big Brother or Nagios. Developping it is not 
really a trouble, but I don't know exactly what checks do I have to perform, what queries send to the machines, ... 

Any clue would be helpful !