This morning another sysadmin in the office restarted our two domain controllers then all of a sudden shit hit the fan. Nobody could log in. The people who were logged in had no chance of doing any work as everything was extremely slow. DHCP stopped working network discovery was failing etc.
When I went to run a wireshark analysis I could see that we were getting almost 100,000 packets a second which is way way more than I would usually from this network. It turned out all the packets were netbios-ns broadcoasts. We powered down the switch this traffic was coming from and then everything worked fine.
Does anybody have any idea what would have caused this issue?