A (Address Record)

The A (Address Record) is one of the most fundamental and commonly used record types in the Domain Name System (DNS). It serves the primary function of mapping a human-friendly domain name to an IP address, specifically an IPv4 address.

Characteristics of an A Record:

  1. Purpose: Maps a domain name to its corresponding IPv4 address.
  2. Format: The record typically consists of a domain name followed by its corresponding IP address.
  3. Example:
    example.com. IN A 192.0.2.1

In this example, when someone browses to example.com, the DNS system will use the A record to resolve example.com to the IP address 192.0.2.1.

Key Points:

  • IPv4 AddressA records deal exclusively with IPv4 addresses. For IPv6 addresses, you’d use an AAAA record (often referred to as a “Quad A” record).
  • Time-to-Live (TTL)Like other DNS records, A records have a TTL value, which specifies how long the record should be cached by DNS resolvers and browsers. Once the TTL expires, the cache will need to be refreshed.
  • Multiple A RecordsIt’s possible for a domain to have multiple A records. This can be used for various purposes, including load balancing and fault tolerance. When multiple A records are set for a domain, DNS servers often rotate the order in which the addresses are returned, effectively distributing the traffic among the different servers.

Using the A record is fundamental for making websites accessible via their domain names and plays a pivotal role in ensuring that the internet remains user-friendly by allowing people to use easy-to-remember domain names instead of numeric IP addresses.

Key terms in plain language

Open a term for a concise explanation of language used on this page.

Fiber Internet

Internet delivered through strands of glass using light. Fiber commonly supports high capacity, low latency, and strong upload performance, but availability must be confirmed for the exact address.

Broadband

A general term for always-on, high-speed Internet access. Broadband can be delivered over fiber, cable, DSL, fixed wireless, cellular, or satellite networks.

Bandwidth

The amount of data a connection can carry in a given time, usually measured in Mbps or Gbps. More bandwidth supports more users, devices, and simultaneous applications.

Latency

The time it takes data to travel between two points. Lower latency improves voice, video meetings, cloud applications, gaming, and other real-time services.

Dedicated Internet Access (DIA)

A business-grade Internet connection with capacity dedicated to the customer rather than shared in the same way as typical consumer broadband. It often includes symmetrical speeds and an SLA.

SD-WAN

Software-defined wide area networking. It manages multiple connections and chooses paths based on application needs, performance, and policy to improve resilience and control.