DNS Update

Question

Good Morning Microsoft Support Team,

We have Virtual Machines provisioned in our Nutanix Prism Central and I happened to clone one of our Linux VMs to create a Test Copy and manually updated the IP Address and the MAC Address of the Cloned Linux VM.

However the DNS Entry (The IP Address of the A Record corresponding to the Original Machine) changed to the IP Address, I had updated for the cloned Linux VM using Linux Network Manager.

I have spoken to Nutanix Support Team and they confirm that it is not a Nutanix Issue and suggested, I log a Support call with Microsoft to investigate this in detail.

Can you please advise on how updating the IP and MAC Address of a Cloned Linux VM cause a DNS Update in our DNS Server hosted in Windows Server 2019 for the Original Linux VM please ?

Regards

Harry

Answer 1

Hello ,

Thank you for posting in Microsoft Community forum.
After you clone a Linux virtual machine and update its IP address and MAC address, the DNS records of the original virtual machine change, which can be related to several factors:

1. If your network uses DHCP servers to assign IP addresses, it can cause DNS records to be updated. When you configure a new IP address for a cloned virtual machine, the DHCP server may associate that IP address with the new MAC address and update the DNS records.
   If the IP address of the original virtual machine is also within DHCP range, the DHCP server may treat it as an available address and update it to the new IP address in the DNS.
2. DNS servers in Windows Server 2019 may be configured to update dynamically. That is, when a DHCP server assigns an IP address, it automatically updates the DNS records.
   If the cloned virtual machine obtains an IP address via DHCP, the DNS server may update the A record of the original virtual machine to reflect the new IP address.
3. Check your network configuration to make sure that no other service is automatically updating DNS records in the background.
4. If the cloned VM conflicts with the DNS records of the original VM, the DNS server may prioritize updating to the latest record.
5. If a DNS update is triggered manually or through a script while updating the IP address of a cloned VM, it may result in the original VM's DNS records being overwritten.

We recommend that you make sure that the settings of the DHCP server do not affect the DNS records of the original virtual machine.
Check the DNS server's logs to see when and why the DNS records were updated.
If possible, consider configuring the original virtual machine with a static IP address to avoid conflicts caused by DHCP.

I hope the information above is helpful.
If you have any questions or concerns, please feel free to let us know.

Regards,
Jill Zhou

Answer 2

Hi Jill Zhou,

Thank you for your explanation.

So in terms of DNS Logs, is there a specific Event IDs, I look at in the Event Viewer ?

I looked for 4662, but I couldnt find any events pertinent to this ID.

Appreciate your help.

Regards

Harry

Answer 3

I'm very sorry that I missed your information.
Thank you for your feedback. Regarding DNS logs, you can search for the following specific event IDs in the Event Viewer of Windows Server 2019 to help you identify the reason for DNS record updates:

Event ID 1000- This is a regular error event for DNS servers that may record errors related to DNS updates.
Event ID 1001- This event ID is usually related to update requests from DNS servers, and you can check if there are any related update records.
Event ID 2501- This event ID indicates that the DNS server successfully updated DNS records, and you can view these events to confirm which records were updated.
Event ID 2502- This event ID indicates that the DNS server failed to update DNS records and may provide clues about the cause of the failure.
Event ID 4013- This event ID indicates that the DNS server failed to start, which may affect the processing of DNS updates.

You can navigate to "Windows Logs" ->"Application and Service Logs" ->"Microsoft" ->"Windows" ->"DNS Server" in the Event Viewer to find these events.

If you cannot find relevant information in these events, it is recommended that you check the configuration of the DNS server to ensure that the dynamic update function is working properly, and check if there are other services or scripts that may affect the update of DNS records.

Best Regards,

Jill Zhou