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Home > Success Center > Network Performance Monitor (NPM) > Managed interfaces -1 index showing as unknown

Managed interfaces -1 index showing as unknown

Updated March 15, 2017


This article provides brief information on managed interfaces showing  -1 indexes are unknown. 

Interface Index (ifIndex) is a unique identifying number associated with a physical or logical interface. For most software, the ifIndex is the name of the interface. Although relevant RFCs do not require the correspondence between particular ifIndex values and their interfaces be maintained across reboots, applications such as device inventory, billing, and fault detection depend on this correspondence.


All NPM versions



Any of the following "sources" can cause interfaces to have -1 ifIndex:

  • Interface remap issue
  • Broken SNMP communication to devices
  • Frequent SNMP timeouts
  • Device reboot can assign different indexes to interfaces


  1. Run SNMPWalk against the device to confirm the interfaces are present.
  2. Log in to your web console as an administartor.
  3. Go to Settings > Node & Group Management > Manage Nodes.
  4. Search the target node.
  5. Expand and select all interfaces currently unknown.
  6. Mark (X) to remove selected interfaces. Click Delete to confirm.
  7. Select More Actions > Rediscover.
  8. Select List Resources and select the target interface.


See the following link to stop the indexes from changing (this applies to Cisco device):

Interface Index (ifIndex) Persistence (© 2017 Cisco, available at, obtained on March 15, 2017.)


Disclaimer: Please note, any content posted herein is provided as a suggestion or recommendation to you for your internal use. This is not part of the SolarWinds software or documentation that you purchased from SolarWinds, and the information set forth herein may come from third parties. Your organization should internally review and assess to what extent, if any, such custom scripts or recommendations will be incorporated into your environment.  You elect to use third party content at your own risk, and you will be solely responsible for the incorporation of the same, if any.





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