Overview
This lecture explains the most important DNS resource record types and how they are used to manage domain name resolutions, load balancing, email delivery, and service configuration.
Basic DNS Resource Record Types
- An A record maps a domain name to an IPv4 address.
- Multiple A records for one domain enable DNS round robin, distributing traffic across multiple IP addresses.
- In round robin, the order of IP addresses returned changes with each DNS query, balancing the load.
- A quad A (AAAA) record is like an A record but maps a domain to an IPv6 address.
CNAME Records
- A CNAME (canonical name) record redirects one domain to another domain.
- Using CNAME avoids duplicating A records, allowing a single update point for IP changes.
- CNAMEs simplify management for domains needing to resolve to the same destination.
MX and SRV Records
- An MX (Mail Exchange) record directs email traffic to a specific mail server for the domain.
- SRV (Service) records specify the location of various services, such as calendar servers, not just mail.
TXT and Other Resource Records
- A TXT (text) record stores arbitrary text data with a domain, originally for human notes.
- TXT records now often convey configuration data for services like email providers.
- NS (Name Server) and SOA (Start of Authority) records define authoritative DNS information for a domain's zone.
Key Terms & Definitions
- A Record — Maps a domain name to an IPv4 address.
- AAAA Record (Quad A) — Maps a domain name to an IPv6 address.
- CNAME Record — Redirects one domain name to another (canonical name).
- MX Record — Directs email traffic to the domain's mail server.
- SRV Record — Specifies the location and details of various services.
- TXT Record — Stores arbitrary, often machine-readable, text data with a domain.
- NS Record — Points to the authoritative name servers for a domain.
- SOA Record — Contains zone information and administrative details for a DNS domain.
Action Items / Next Steps
- Review DNS record types and their use cases.
- Practice configuring A, CNAME, MX, SRV, and TXT records for different domain scenarios.