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Why does ONTAP initiate a connection on a port other than 4045 for for NLM callbacks?

Last Updated:

Applies to

  • ONTAP 9
  • UNIX or UNIX-like operating system
  • NFSv3
  • Network Lock Manager (NLM)


  • Clients request NLM locks with requests sent to ONTAP on port 4045.
  • If a blocking lock cannot be granted immediately, ONTAP will later send a callback to the client when the lock is granted.
  • The callback will be done from ONTAP to the client using a port discovered using the port mapper.

Additional Information

The NLM port used by ONTAP can be configured using nfs option modify -nlm-port.
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