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Diagnosing a broadcast storm?

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Last Modified: 2015-03-30
Hello experts,

   We are having a strange occurrence on our network that I'm hoping to get some help in diagnosing. We are having random computers "lock up" where we can not even ctr-alt-del, they need to be hard rebooted. All computers have been scanned with Malwarebytes, Vipre, and Combofix with no threat results. We have rewired the network and replaced all switches to ensure no loops. Also, STP is enabled. I have been trying to determine what the source is through packet captures.

   When running packet captures there were 4 devices sending out a constant ARP request for the two IPs of 10.0.0.202 and .203. These two IPs do not seem to exist anywhere on the network. They are not in a DHCP scope and return no pings, and I can not find anything with them statically assigned. This network contains one router and multiple switches, all on the same 10.0.0.0/24 subnet, there are no VLANs. Three of the four devices sending out these constant ARP requests were Windows 7 PCs. I have since disconnected them from the network, and the issues seem to have gone away, for now.

  However, when running a capture I still see the DNS Server (.100), running 2012 R2 is still sending out ARP requests to the same IPs, constantly. I am not sure what is causing this, any help is greatly appreciated. Thanks in advance.

00:28:13.040905 ARP, Request who-has 10.0.0.203 tell 10.0.0.100, length 46
00:28:13.040951 ARP, Request who-has 10.0.0.202 tell 10.0.0.100, length 46
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