I had the exact same issue this morning as described by requester. DHCP services fell down on their knees and IPv6 enabled desktops bombarded the core switchs with DHCP request flooding them rendering them unresponsive.. hey ! a neat DELL stack on it...

Running Lansweeper on Windows 10, following latest update I experienced this exact same issue.Running 2 firsts steps, then restarting "IIS Express service" service did the trick !Thank you !