Azure VM cannot reach DNS server / domain network
I am trying to join an Azure VM to the SMX domain.
I have configured the DNS servers on the VM to use the SMX domain DNS servers. However, the VM is unable to reach these DNS servers. Also unable to ping DNS servers.
1 answer
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Thanmayi Godithi 10,655 Reputation points • Microsoft External Staff • Moderator
Hi Lily Wang (BEYONDSOFT CONSULTING INC), thank you for sharing the additional details and the effective routes screenshot.
Based on all the information provided, we can now clearly identify the root cause of the issue.
The DNS servers (10.184.232.13 / 10.184.232.14) are hosted in your on-prem SMX network. However, the Azure Virtual Network where your VM resides does not currently have any connectivity to the on-prem network.
From your inputs:
- ExpressRoute is not configured
- The VPN connection is from your laptop only (Point-to-Site), which does not extend to the Azure Virtual Network
- The effective routes on the VM do not show any route for the on-prem subnet (10.184.232.0/24)
Because of this, the Azure VM has no network path to reach the on-prem DNS servers, which is why:
- Ping to the DNS server fails
- Port 53 connectivity fails
- DNS resolution (nslookup) fails
- Domain join cannot proceed
The issue is due to missing hybrid connectivity between Azure Virtual Network and the on-prem SMX network.
To resolve this, you will need to establish connectivity between Azure and your on-prem network using one of the following:
- Site-to-Site VPN (recommended)
- ExpressRoute
Once this is configured:
- The on-prem network (10.184.x.x) will be reachable from Azure
- Routes to the on-prem subnet will appear in the effective routes
- The VM will be able to communicate with the DNS servers
- Domain join should succeed
Kindly let us know if the above helps or you need further assistance on this issue.
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