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Avamar NDMP backup fails with "unable to establish data connection"

Last Updated:

Applies to

DELL Avamar


  • In a NDMP backup using a remote or 2-way topology, the first connection established is the NDMP control connection
  • The DMA and the NDMP Server exchange requests and responses on the control connection
  • The NDMP data connection is a separate connection used to send backup data from the NDMP Server, over the network, back to the DMA and the DMA's storage.
  • In this scenario, the control connection is successful, but the data connection to the DMA (Avamar) is never established.
  • In the ndmpd debug log and Avamar log, bi-directional requests and responses can be observed over the control connection
  • The ndmpd debug log shows a LIF is selected for the ndmp data connection and a connection attempted, but the data connection is never established
  • The inability to establish a data connection suggests a device or configuration on the network path blocking the connection
  • Because the connection from the NDMP Server back to Avamar is never established,  the DMA eventually times out and closes the NDMP session.
  • AVFirewall had previously been identified as the cause of data connection issues and was disabled

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