Unable to Connect Log Analytic Agent to Log Analytic Workspace via custom DNS Server

Question

Hi all,

When I am connecting log analytic agent to log analytic workspace via azure provided dns server, it is working fine, however when I changed the dns server to a custom one, then it failed with following message:

[{"heartbeat":{"code":12007,"formattedMessage":{"lang":"en-US","message":"DNS name resolution of the Microsoft Operations Management Suite service failed. This could be due to either the Workspace ID being configured incorrectly, or the agent not having Internet access. Please check that the system either has Internet access, or that a valid HTTP proxy has been configured for the agent."},"status":"notready"},"timestampUTC":"2021-09-19T19:50:03.6117325Z","version":"1.0"}]

if I try to run the built in '.\TestCloudConnection.exe', i got following error:
Firewall troubleshooting details: "The remote name could not be resolved: 'loganalyticid.oms.opinsights.azure.com'"

The vm machine has internet connection as I have tested with ping google.com, and it is fine.

I have been searching for online for solutions but so far no luck, also I have ensured the firewall is turned off, and network security group has the internet outbound connectivity.

The only way to make it work is when I use azure provided dns server, such as following:

That means there is some configurations that I need to do in order to allow the custom dns server to resolve the remote name *.oms.opinsights.azure.com

Any guidance on this would be appreciated, Thanks.

Answer 1

<<Converting the information from comments to here for broader community usage>>

@Qi-Jian-Huang-DevOps - Thank you for reaching out with your query.

Please follow through below documentation related custom DNS configuration and troubleshooting scenarios.

https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-name-resolution-for-vms-and-role-instances#vms-and-role-instances
https://learn.microsoft.com/en-us/azure/azure-monitor/agents/agent-windows-troubleshoot#important-troubleshooting-sources

Hope this information helps. Let us know if you have any further queries. Thank you