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Home > Success Center > IP Address Manager (IPAM) > Empty MAC from Neighbor Scans causes IPs to be flagged as Used

Empty MAC from Neighbor Scans causes IPs to be flagged as Used

Updated December 14, 2016


This article pertains to an issue that can happen where IPs that are not in use are being flagged as Used when a Neighbor Scan on the subnet finds an IP entry in the ARP cache of the scanned device that has an empty MAC or 00-00-00-00-00-00.


IPAM 4.3.2 and lower: Resolved below

IPAM 4.5 and higher: In progress


This issue is caused when IPAM mistakenly takes the empty MAC as a true MAC and considering the IP entry in the cache to be in use. 


  1. Upgrade to IPAM 4.3.2.
  2. Stop all Orion services through the Orion Service Manager.
  3. On the IPAM server, navigate to Program Files (x86)\SolarWinds\Orion\IPAM.
  4. Find and edit the file named SolarWinds.IPAM.Jobs.dll.config.
  5. Search for the line like so
    <add key="NeigborScanJob.SkipEmptyMAC" value="False" />
  6. Change the value from False to True.
  7. Save the file.
  8. Restart the services.
  9. This will cause IPAM to automatically skip all IPs in the arp cache that has an empty MAC.


For IPAM 4.5 and higher, this issue was to be fixed in 4.6, but an issue has occurred making it not possible to add the setting. This is currently being investigated and will be updated asap.




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