AZ-700 Question 31
Single answerYour company owns the domain contoso.com, which is registered and hosted by a third-party provider. You want to isolate DNS records for a new subdomain, dev.contoso.com, in Azure DNS so that it can be managed independently. How should you ensure the dev.contoso.com subdomain is publicly resolvable using Azure DNS?
- A
Create a new public DNS zone named contoso.com in Azure DNS and add an A record for dev.contoso.com to that zone.
- B
Create a new public DNS zone named dev.contoso.com in Azure DNS and add the Azure DNS name servers as an NS record in the contoso.com zone at the third-party provider.
- C
Create a new private DNS zone named dev.contoso.com in Azure DNS and associate it with your virtual network for external queries.
- D
Modify the TTL for contoso.com at the third-party provider to forward all queries for dev.contoso.com to Azure DNS.
Show answer and explanation
Correct answer: B
Explanation
In Azure DNS, delegating a subdomain like dev.contoso.com to a separate DNS zone requires two key steps: first, create a public DNS zone for dev.contoso.com in Azure DNS; second, configure the parent zone (contoso.com) to have an NS record pointing to the Azure name servers. This process ensures that queries for dev.contoso.com are sent to Azure DNS, allowing you to manage DNS records independently. For more details, refer to the official Microsoft documentation on delegating subdomains: https://learn.microsoft.com/azure/dns/dns-delegate-subdomain.
- A. Incorrect.
Incorrect. Simply creating a zone for contoso.com in Azure DNS and adding an A record for dev.contoso.com does not properly delegate the subdomain. The root domain is still hosted by the third-party provider, so DNS queries for dev.contoso.com would not automatically be directed to Azure DNS.
- B. Correct.
Correct. Creating a dedicated public DNS zone for dev.contoso.com in Azure DNS and configuring an NS record in the parent contoso.com zone at the third-party provider delegates the subdomain. This allows external queries to resolve dev.contoso.com through Azure DNS name servers.
- C. Incorrect.
Incorrect. Private DNS zones only resolve names within selected virtual networks. They are not publicly accessible over the internet, so dev.contoso.com would not resolve outside the network.
- D. Incorrect.
Incorrect. Updating the TTL does not delegate the subdomain to Azure DNS. Proper delegation requires creating an NS record in the parent zone pointing to the Azure DNS name servers for dev.contoso.com.