Azure Private DNS Zone resolution

Question

Hi folks,

Hope you are doing well!

I have a doubt with regards to Azure Private DNS and Custom DNS Servers in Vnets as below:

As far I understand, if we are specifying custom DNS servers in Vnets then even Azure PaaS related private DNS zone resolution (let's say for Blob or File etc.) will be redirected to the custom DNS servers bypassing Azure DNS, then I will have to setup conditional forwarders to be able to resolve them. Is my understanding correct?

Now, what if I want my both of the setup work together, i.e. I want my Vnets to refer to my custom DNS servers as well as I want PaaS services resolutions to be redirected to Azure DNS.

Can this be achieved if I specify '168.63.129.16' as a custom DNS server in the Vnet? Apologies if this sound non-sensical/ silly but just wanted to clarify my doubt.

Also, is there any order of precedence in the custom DNS servers specified in the Vnets.

Thanks in advance!

Regards

Answer 1

@Apurva Pathak ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

Wrt,

As far I understand, if we are specifying custom DNS servers in Vnets then even Azure PaaS related private DNS zone resolution (let's say for Blob or File etc.) will be redirected to the custom DNS servers bypassing Azure DNS, then I will have to setup conditional forwarders to be able to resolve them. Is my understanding correct?

• Yes
• This is correct.

Your requirement :

Now, what if I want my both of the setup work together, i.e. I want my Vnets to refer to my custom DNS servers as well as I want PaaS services resolutions to be redirected to Azure DNS.

Wrt,

Can this be achieved if I specify '168.63.129.16' as a custom DNS server in the Vnet? Apologies if this sound non-sensical/ silly but just wanted to clarify my doubt.

• It is technically possible to define '168.63.129.16' as a custom DNS server in the VNet.
• This will work but not as you expect.
• It is because, as you mentioned, there is a order of precedence in the custom DNS servers specified in the VNet.
• The order is the DNS servers specified in the VNET DNS configuration page.
• See : DNS servers of a virtual network
  • 
  • What this means is that as long as the first DNS server is reachable, Azure will continue to use it even if it gives wrong or null response to the DNS Query.

Kindly let us know if this helps or you need further assistance on this issue.

Thanks,

Kapil

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Answer 2

Hi @Apurva Pathak ,

if I got your requirement right you want to use your custom DNS in combination with Azure private DNS.

If my assumption is right it works the follows:

Configure your custom DNS Server IP in the Custom DNS Settings of the vNets (not the Azure DNS IP!).

Add a conditional forwarder on your custom DNS Server to an Azure Private Resolver

Please take a look here: Azure Private Resolver with on-premises DNS forwarder

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Regards

Andreas Baumgarten