Unity: Two Production Interfaces on NAS Server May Cause Intermittent DU if One is Not Set to Preferred-User Correctable

Summary: Having two production interfaces on one NAS server may cause intermittent data unavailability (DU) if not configured properly.

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Symptoms

Intermittent DU - users cannot resolve the shares' Fully Qualified Domain Name (FQDN) from the Domain Name System (DNS)

There are two interfaces configured with the role of Production on the NAS server in question.

A preferred interface is not configured for the NAS server to use for outbound connections like DNS, Kerberos, and Lightweight Directory Access Protocol (LDAP) requests.

Cause

If there are two interfaces configured with a role of Production on the NAS server (as shown below) and one is meant to connect to the DNS and allow access to file systems and shares while the other is meant for backups and Disaster Recovery (DR) testing, this may result in the preferred interface flapping between the two interfaces configured with the role of Production.

 If the route count is equal and interfaces all have a gateway defined, the first interface in the list is picked as the preferred interface. This appears to favor interfaces with lower octet values and may result in a switch to a newly added interface.

Screenshot of NAS properties and configured interfaces

Resolution

There are two possible fixes available depending on the circumstances:

  • Open the UI > File > NAS Servers > Network

From here, you can click (upper right) - Change Preferred Interface. 

In here, you see what is set as the current Preferred interface but this can change at any time. If the route count is equal and interfaces all have a gateway, the first interface in the list is picked as the preferred interface. This appears to favor interfaces with lower octet values and can result in a switch to a newly added interface.

In here, change the interface you want to use that is configured for outbound connections to things like DNS, Kerberos, or LDAP connections, then click OK. This sets the preferred interface, and there is not downtime needed for this:

 

Screenshot of preferred interface

 

  • If one of these interfaces is to be set up for backups or DR testing, then change the roles to suit the correct function of that interface. Open the UI > File > NAS Servers > Network > Delete the interface that is set as Production that is supposed to be set to Backup and DR Testing and re-create this so the roles match the function of the Interface. See the example below:

Screenshot of NAS properties and configured interfaces

Affected Products

Dell EMC Unity 300F, Dell EMC Unity 350F, Dell EMC Unity 400, Dell EMC Unity 400F, Dell EMC Unity 450F, Dell EMC Unity 500, Dell EMC Unity 500F, Dell EMC Unity 550F, Dell EMC Unity 600, Dell EMC Unity 600F

Products

Dell Unity 300, Dell EMC Unity XT 380, Dell EMC Unity XT 380F, Dell EMC Unity XT 480, Dell EMC Unity XT 480F, Dell EMC Unity 650F, Dell EMC Unity XT 680, Dell EMC Unity XT 680F, Dell EMC Unity XT 880, Dell EMC Unity XT 880F , Dell EMC Unity Family |Dell EMC Unity All Flash, Dell EMC Unity Family, Dell EMC Unity Hybrid ...
Article Properties
Article Number: 000219787
Article Type: Solution
Last Modified: 12 ديسمبر 2025
Version:  3
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