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Best Practice for Kerberos AES Settings with ONTAP

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Applies to

  • ONTAP 9
  • Cloud Volumes ONTAP (CVO)
  • CIFS/SMB with Kerberos authentication
  • Active Directory (AD)

Description

NetApp best practice is to use AES for ONTAP SMB Kerberos communication and to move away from RC4 as part of standard AD hardening.

For modern environments, the preferred ONTAP Kerberos posture is:

  • AES-128 and AES-256 enabled
  • RC4 disabled where the ONTAP release and surrounding Active Directory environment support it
  • DES not used

This approach aligns with current ONTAP documentation, NetApp KB guidance, and Microsoft's direction to move Active Directory away from RC4.

  •  On ONTAP 9.12.1 and later, customers should explicitly configure the SMB server to advertise only AES encryption types after validating that domain controllers, clients, and related service paths support AES.
  • On ONTAP 9.11.1 and earlier, AES should still be enabled where possible, but RC4 advertisement cannot be fully disabled, so customers with a strict RC4-removal requirement should plan an upgrade.

Enabling AES is generally low risk in a healthy environment because existing SMB sessions are not disrupted and only new Kerberos authentications negotiate the stronger encryption type. The main operational consideration is that changing the AES setting resets the SMB server machine account password in Active Directory, which can require OU-level administrative credentials and should be handled through a maintenance window.

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NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.