Duplicate SRV records are cousing domain join workflows to fail

Have you ever had problems with duplicate SRV records in your environment? This is a quite common phenomenon when you google it without any real solution to it (not at least what I could find). Some environments would not be affected by this, but I got into a specific situation recently where some workflows in Nutanix would fail because of duplicate SRV records.

Symptoms:

  • Duplicate SRV records, one in lower-case – one in upper-case, are causing some workflows in Nutanix to fail.
  • When deleting the oldest record the duplicate is just recreated after some period of time (like 30 minutes or so).

So whats cousing this? In this specific case we managed (together with Microsoft support) to isolate the issue and found out that there were two main things that were related to this behaviour listed below.

Causes:

  • Some Domain Controllers names were in lower-case, others in upper-case.
  • When you have a mixture of DNS servers running Windows Server 2012 and 2016 the way that machine names are registered differs between those Windows versions.

So how do we solve this? The preferred solution from Microsoft was to rename all domain controllers to lowercase, but since all Domain Controllers except one, in this case, was in uppercase we tried to rename that specific DC to uppcase instead. The following steps were performed on the server:

    1. Demote DC
    2. Rename to uppercase
    3. Promote DC
    4. Delete all duplicated SRV records in DNS
    5. (If  the issue is still happening):
      1.  Stop netlogon service
      2. Delete C:\Windows\System32\config\netlogon.dnb
      3. start netlogon service

After doing this the duplicate SRV records stopped being recreated in the environment.

Resolution:

  • The preferred way to solve the issue is to rename all domain controllers to lowercase (or uppercase which works too).

If you have any questions, feel free to email me at tobias.sandberg@xenit.se or comment down below. I will try to answer you as soon as possible.

Disclaimer: All information on this blog is offered "as is" with no warranty. It is strongly recommended that you verify all information and validate all scripts in isolated test environments before using them in production environments.