hi i want to discover all the dhcp server currently available on LAN
closed as not a real question by jscott, Ward, Lucas Kauffman, mailq, Tim Brigham Jul 29 '12 at 0:17
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DHCP requests are limited to a broadcast domain - i.e. subnets delimited by routers, unless you have something like IP helper setup on the router. So using some kind of network level discovery method, you will never know for sure if you got them all, unless you connect to every subnet.
You could use Wireshark or Network Monitor to view the network traffic in each of your broadcast domains - every DHCP server in a broadcast domain should respond to a DHCP request, even though the client will only handle the first response it recieves.
Try DHCP Explorer, of course it'll only find servers on segments it's ran against, not 'all' as DHCP isn't routed by default.
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