Setting Up Microsoft Active Directory

In distributed enterprise environments, Active Directory (AD) configuration often becomes the silent culprit behind authentication instability and slow SMB response times. AD plays a critical role in ensuring secure, seamless authentication for users accessing file shares on CTERA Edge Filers. A clean, correctly mapped AD environment and well-structured AD configuration is essential for both performance and stability of your file system.

The following outlines the CTERA recommended best practices for setting up Active Directory in environments with CTERA Edge Filers.

Ensure Reliable Network Connectivity

A stable connection between the CTERA Edge Filer and domain controllers is the foundation for AD health.

Monitor WAN usage – If WAN links hit 100% utilization, AD authentication may fail.
Correlate AD disconnects with bandwidth usage – Check the CTERA Edge Filer system log for AD disconnects, then compare these with network monitoring tools.

Validate Active Directory Sites and Services

CTERA Edge Filers should only be associated with one AD domain at a time. Duplicate or stale records in AD can cause failed lookups and authentication delays. CTERA recommends the following best practices.

• Remove duplicate A records and PTR records for the edge filer in the wrong domain.
  • In DNS Manager go to Forward Lookup Zones
    
    For your domain, search for the edge filer name and delete stale A records and duplicate PTRs in Reverse Lookup Zones.
    
  Note

  You can access DNS Manager from Server Manager > Tools.
  

• Verify the edge filer hostname resolves only within the correct domain’s namespace.
  • In a Windows client command prompt, run nslookup <edgefiler_ip> and confirm the FQDN returned matches only the expected domain.
    
• Confirm the correct site association in Active Directory Sites and Services for the device subnet.
  • In Active Directory Sites and Services go to Subnets.
    
    Verify the edge filer’s subnet assignment. Ensure it’s assigned to the proper site, and that the site lists the expected local domain controllers being used as DNS by the CTERA Edge Filer.
  Note

  You can access Active Directory Sites and Services from Server Manager > Tools.
  

DNS Configuration Must Match AD

DNS misconfigurations are one of the most common root causes of AD authentication failures.

• Point the edge filer to DNS servers that are also domain controllers for the correct AD site.
• Do not mix in external DNS resolvers or incorrect site domain controllers.

Check Firewall and Port Access

AD authentication requires multiple protocols to function correctly. Make sure the following ports are open between the edge filer and domain controllers:

Inbound Ports

Outbound Ports

For a ports diagram and more ports information, see Edge Filer Ports Diagram.

Keep Time Synchronized

Kerberos authentication is extremely sensitive to clock skew. Ensure:

• The edge filer is syncing time with the same NTP source as your domain controllers.
• Maximum time drift allowed is 5 minutes—but CTERA recommends keeping 30 seconds.

Clean Up Stale AD Objects

When moving devices between domains or sites, stale objects can linger. This leads to trust issues and failed authentication.

• Search for old edge filer computer objects in AD and remove them.
• Re-join the device cleanly to the intended domain.

Validate Authentication Flow

Once cleanup is complete, test the authentication flow:

• From the edge filer, confirm that a domain connection is successful
• Ensure users can log in without delay.
• Ensure a stable connection pattern over multiple days, if a connection is unstable there is additional AD tuning that can be done.