Observability

NetFlow v9 Flows Not Processed Due to Missing Required Fields (InterfaceRx/InterfaceTx) in SolarWinds NTA

SolarWinds NTA generates alerts indicating that NetFlow data is being received but cannot be processed due to missing required fields in the NetFlow v9 template. Additionally, interfaces sending flow data are not managed or monitored in SolarWinds, leading to visibility gaps in traffic analysis.

First published date

5/6/2026 4:05 PM

Last published date

5/6/2026 4:05 PM

Overview

This issue occurs when the exporting device does not include mandatory fields required by SolarWinds NTA:

InterfaceRx (Input Interface Index)
InterfaceTx (Output Interface Index)

Without these fields, NTA cannot map traffic correctly to interfaces. Additionally, alerts appear when flow data is received from interfaces not added or enabled for monitoring.

Product section

Hybrid Cloud Observability

Resolution

Verify NetFlow export configuration on the device and ensure it is sending data to the SolarWinds NTA server IP with the correct port (default UDP 2055)
Ensure the NetFlow v9 or Flexible NetFlow template includes required fields:
- InterfaceRx (Field Type 10)
- InterfaceTx (Field Type 14)
Update or modify the flow record configuration on the device to include input and output interface fields
Confirm that NetFlow templates are being exported correctly; restart the flow export process if needed to refresh templates
Add unmanaged interfaces in SolarWinds by navigating to the node and selecting Add this interface or managing interfaces manually
Enable NetFlow analysis on the required interfaces within SolarWinds NTA
Verify that required firewall ports (e.g., UDP 2055) are open between the device and the SolarWinds server
Validate flow data in the NTA Summary page and confirm that traffic is properly displayed per interface

Additional Notes:

Devices lacking support for the required NetFlow fields may not be fully compatible with NTA
A firmware upgrade may be required on certain Cisco devices
Reference: Required fields in SolarWinds NTA

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