How to Test DNS SRV

Use nslookup to verify DNS SRV records.

DNS service locator records, or SRV records, are used by Domain Naming Services (DNS) to locate computers that host specific services. In a Microsoft Active Directory environment, SRV records are used to locate domain controllers. When Active Directory services are first installed on a server, the installation process adds the appropriate SRV records to the DNS server automatically. To verify that the records were created successfully, you can use the graphical DNS Management snap-in or, if you prefer to use the command line, you can use "nslookup."

Things You'll Need

• computer with Windows 2000 or higher

Instructions

Method 1: Using the DNS Management Tool to Test Srv Records

1. Open the "DNS Management" tool on your DNS server by typing "dnsmgmt.msc" into the "Run" command and pressing "OK."

2. Click on the plus sign next to the "Forward Lookup Zones" node to expand that folder.

3. Navigate to the following two DNS folders and verify that the "_kerberos" and "_ldap" service records exist in each. Make sure to substitute the name of your domain for [domain_name] in the folder names:

   Folder 1: [domain_name]/_msdcs/dc/_sites/Default-First-Site-Name/_tcp.

   Folder 2: [domain_name/_msdcs/dc/_tcp

Method 2: Using NSLookup to Test DNS Srv Records

1. Open a command prompt by clicking on the "Start" menu and typing "cmd" into the "Run" command.

2. Type "nslookup" at the command prompt and press "Enter" on your keyboard.

3. Type "set type=SRV" at the nslookup prompt and press the "Enter" key.

4. Type "_ldap._tcp.dc._msdcs.[domain_name] and press "Enter," making sure to replace [domain_name] with the name of your own domain.

5. Verify that at least one resource record was returned. The record will list the fully qualified domain name of the domain controller computer along with its IP address.

6. Type "Exit" to exit nslookup and type "Exit" again to close the command prompt window.

Tips & Warnings

• If you are using a non-Windows DNS Server to support Active Directory, you can verify SRV records by checking the "netlogon.dns" file, which is located in the "%systemroot%\config" folder located on the domain server.

• Modifying DNS records can interrupt network operations. Only make changes if they are absolutely necessary and only if you understand the ramifications of the change.

References

• Microsoft Technet: Verifying Your Basic DNS Configuration