5.1.5.1. Configure Azure DNS Zones and Record Sets

💡 First Principle: An Azure DNS zone acts as a container for a domain's DNS records, and configuring these records is the fundamental act of mapping human-readable domain names to the IP addresses and services that power them.

Scenario: You need to host the public DNS records for your company's main website (www.contoso.com) and its mail servers (mail.contoso.com) in Azure DNS. You need to ensure the website points to your Azure Load Balancer's public IP and mail traffic is correctly directed.

What It Is: An Azure DNS zone is a logical container for all the DNS records for a particular domain name.

Common DNS record types in Azure DNS zones:

• A record: Maps a domain name to an IPv4 address.
• AAAA record: Maps a domain name to an IPv6 address.
• CNAME record: Maps an alias to another canonical domain name.
• MX record: Specifies mail servers for a domain.
• TXT record: Stores arbitrary text, often used for SPF or domain verification.
• NS record: Lists the authoritative name servers for the DNS zone.
• SOA record: Contains administrative information about the zone.

TTL (Time-to-Live): TTL defines how long DNS records are cached.

⚠️ Common Pitfall: Using a CNAME record at the root (apex) of a domain (e.g., contoso.com). This is not allowed by DNS standards. For the root domain, you must use an A record or an Alias record (an Azure DNS specific feature).

Key Trade-Offs:

• A Record vs. CNAME Record: An A record points directly to an IP address, which can become stale if the IP changes. A CNAME points to another DNS name, which is more flexible if the underlying IP of the target service changes.

Reflection Question: How does configuring Azure DNS zones and various record types (e.g., A, CNAME, MX) fundamentally ensure domain names are accurately mapped to the correct IP addresses and services, supporting reliable resource discovery and web/email functionality?