Dell Unity 480 (v5.3) - SMB Issues with Windows Server 2025 Domain Controllers

Hi everyone,

I am facing a critical issue after migrating our Domain Controllers from Windows Server 2016 to Windows Server 2025, and I would appreciate any insight from the community.

Environment:

• Storage: Dell Unity 480 (Firmware: 5.3.0.0.5.120)

• Infrastructure: ~250 PCs/Users accessing SMB shares (Folder Redirection and Group Shares).

• The Issue: Since the upgrade to Domain Controller Server 2025, the Unity reports: "The NAS server NASPLAN in the domain bncf.local can't reach any Domain Controller." The shares are marked as "Degraded" in the Unity Unisphere.

Current Status: Surprisingly, the system is still "working" in production: users can currently access the shares, but the Unity cannot establish a fresh management/trust connection with the new DCs. I fear that as soon as Kerberos tickets expire or a reboot occurs, everything will fail.

Technical Analysis:

• Dell Support: After a network trace analysis, Dell concluded the issue is on the Unity side. Kerberos authentication seems to succeed, but the SMB dialogue fails to complete.

• SMB Signing: It appears the new Server 2025 DCs enforce SMB Signing, and the Unity is tearing down the session during the handshake.

• Deep Dive: I checked the advanced CIFS/SMB parameters via CLI and found this:

name                    = smbsigningfacility_name           = cifsdefault_value           = 1current_value           = 1configured_value        = 1param_type              = NAS serveruser_action             = restart NAS Serverchange_effective        = restart NAS Serverrange                   = (0,1)description             = Manages SMB signing on the NAS server

The Dilemma: The Unity has an uptime of 500+ days. This parameter (smbsigning = 1) is not visible in the GUI and seems to be "pending" a restart to actually take effect.

My Concerns:

1. Is the fact that the parameter hasn't been "applied" (due to the 500-day uptime) the reason why the Unity is failing to negotiate SMB signing with the 2025 DCs?

2. I am terrified of restarting the NAS Server. If the "Join" fails after the restart, 250 users will be offline.

Questions:

• Has anyone encountered specific SMB/Kerberos compatibility issues between Unity OE 5.3 and Windows Server 2025?

• Should I try to manually toggle the smbsigning parameter or force a NAS Server restart?

• What is the safest way to re-establish the trust relationship without losing the existing ACLs/permissions on the shares?

Thank you in advance to anyone who can spare a few minutes to help with this.