A hosted zone in AWS Route 53 is essentially a container for DNS records for a domain. Each hosted zone corresponds to a domain name, and it contains various DNS records that define how requests for that domain should be routed. There are two main types of hosted zones:

1. Public Hosted Zone: Used for managing DNS records for domain names that are publicly accessible on the internet.
2. Private Hosted Zone: Used for managing DNS records for domain names within a VPC (Virtual Private Cloud), making them accessible only within that VPC.

Common DNS Records in Route 53 Hosted Zones

1. A (Address) Record

   • Purpose: Maps a domain name to an IP address (IPv4).
   • Example: example.com → 192.0.2.1
   • Use Case: Commonly used to point your domain to a web server's IP address.

   Name: example.com
   Type: A
   Value: 192.0.2.1
   
   

2. AAAA (IPv6 Address) Record

   • Purpose: Maps a domain name to an IPv6 address.
   • Example: example.com → 2001:0db8:85a3:0000:0000:8a2e:0370:7334
   • Use Case: Used when you want to point your domain to a server that supports IPv6.

   Name: example.com
   Type: AAAA
   Value: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
   
   

3. CNAME (Canonical Name) Record

   • Purpose: Maps a domain to another domain name (like an alias).
   • Example: www.example.com → example.com
   • Use Case: Often used to point subdomains to a main domain (e.g., www.example.com to example.com).

   Name: www.example.com
   Type: CNAME
   Value: example.com
   
   

4. MX (Mail Exchange) Record

   • Purpose: Specifies the mail servers responsible for receiving email on behalf of your domain.
   • Example: example.com → mail server mail.example.com
   • Use Case: Required for setting up email services.

   Name: example.com
   Type: MX
   Value: 10 mail.example.com
   
   

   • Explanation: The number 10 is the priority of the mail server. Lower values indicate higher priority.

5. TXT (Text) Record

   • Purpose: Allows you to store text information associated with a domain.
   • Example: example.com → "v=spf1 include:_spf.google.com ~all"
   • Use Case: Often used for SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), or verification with third-party services (like Google or Microsoft).

   Name: example.com
   Type: TXT
   Value: "v=spf1 include:_spf.google.com ~all"
   
   

6. NS (Name Server) Record

   • Purpose: Defines the authoritative name servers for the domain. Every domain has at least two NS records, pointing to servers that handle the domain's DNS queries.
   • Example: example.com → ns-1234.awsdns-56.org, ns-789.awsdns-34.co.uk
   • Use Case: Required for domain registration, delegating authority to the nameservers.

   Name: example.com
   Type: NS
   Value: ns-1234.awsdns-56.org
   
   

7. ALIAS Record

   • Purpose: Similar to a CNAME record but used for root domain records (e.g., example.com) and AWS-specific resources (like S3 buckets, CloudFront distributions, etc.). It avoids the CNAME restriction for the root domain.
   • Example: example.com → S3 bucket example-bucket.s3-website-us-east-1.amazonaws.com
   • Use Case: Ideal for pointing your root domain (e.g., example.com) to an AWS resource.

   Name: example.com
   Type: A (ALIAS)
   Value: example-bucket.s3-website-us-east-1.amazonaws.com
   
   

8. SRV (Service) Record

   • Purpose: Specifies the location of servers for specified services, such as for SIP or XMPP.
   • Example: _sip._tcp.example.com → _sip._tcp.sipserver.example.com
   • Use Case: Used to specify the location of servers for specific services like VoIP.

   Name: _sip._tcp.example.com
   Type: SRV
   Value: 10 60 5060 sipserver.example.com
   
   

9. PTR (Pointer) Record

   • Purpose: Maps an IP address to a domain name (reverse DNS lookup).
   • Example: 192.0.2.1 → host.example.com
   • Use Case: Used for reverse DNS lookups, often by email servers to verify the identity of a domain.

   Name: 1.2.0.192.in-addr.arpa
   Type: PTR
   Value: host.example.com
   
   

Example Scenarios for DNS Records:

1. Web Hosting:
   • Root Domain: You can point example.com to an EC2 instance using an A record or an ALIAS record for AWS resources.
   • Subdomain: www.example.com → example.com (using CNAME) or redirecting with an A record.
2. Email Setup:
   • To use Gmail or another email provider, you would configure MX records for example.com to specify the mail servers that will handle emails for your domain.
3. Subdomain Delegation:
   • If you want a subdomain (sub.example.com) to be handled by another DNS provider, you would add NS records to point to the external DNS servers.
4. Content Delivery Network (CDN):
   • Pointing a root domain or subdomain to a CloudFront distribution can be done with an ALIAS record. For example, cdn.example.com → d1234567890abc.cloudfront.net.
5. Third-Party Service Integration:
   • Adding a TXT record for SPF to prevent email spoofing: "v=spf1 include:_spf.google.com ~all".