A Record
A DNS record type that maps a hostname to an IPv4 address. The most fundamental DNS record, used by CDNs to direct users to the nearest edge server via Anycast or geo-based DNS resolution.
Full Explanation
An A record is the most basic DNS record. It takes a hostname like example.com and points it to an IPv4 address like 93.184.216.34. When your browser needs to reach a website, the DNS resolver returns an A record, and your browser connects to that IP.
For CDNs, A records are central to how traffic gets routed. When you onboard a domain to a CDN, the CDN either gives you an Anycast IP (one IP, many servers) or uses geo-DNS to return different A records depending on the resolver's location. A user in Tokyo gets a different IP than a user in London, each pointing to the closest edge server.
The TTL (Time to Live) on an A record controls how long resolvers cache the answer before asking again. CDNs typically use low TTLs (30 to 300 seconds) so they can shift traffic quickly during failover or load balancing changes. Your marketing site might use a 3600-second TTL because it rarely changes. A CDN's DNS-based load balancer might use 30 seconds.
One hostname can have multiple A records. This is called a round-robin setup. The resolver hands out all of them, and the client picks one (usually the first). CDNs sometimes use this as a basic load distribution mechanism, but Anycast is more common at scale because it routes at the network layer rather than relying on DNS.
If you're debugging CDN routing, the A record is your starting point. You can check what IP a domain resolves to from different locations and verify it maps to the expected CDN edge. Tools like dig, nslookup, and online DNS checkers let you query A records from multiple vantage points.
A records only support IPv4. For IPv6, you need AAAA records. Most CDNs serve both, giving you dual-stack coverage so clients on either protocol can reach the nearest edge.
Examples
# Query A record for a domain
dig example.com A +short
# Output: 93.184.216.34
# Query with full details including TTL
dig example.com A
# ;; ANSWER SECTION:
# example.com. 3600 IN A 93.184.216.34
# Check what CDN a domain is using via A record
dig www.shopify.com A +short
# Returns Cloudflare Anycast IPs like 104.16.x.x
# Query from a specific DNS server
dig @8.8.8.8 example.com A +short
# Multiple A records (round-robin)
dig loadbalanced.example.com A +short
# 192.0.2.1
# 192.0.2.2
# 192.0.2.3Frequently Asked Questions
A DNS record type that maps a hostname to an IPv4 address. The most fundamental DNS record, used by CDNs to direct users to the nearest edge server via Anycast or geo-based DNS resolution.
# Query A record for a domain
dig example.com A +short
# Output: 93.184.216.34
# Query with full details including TTL
dig example.com A
# ;; ANSWER SECTION:
# example.com. 3600 IN A 93.184.216.34
# Check what CDN a domain is using via A record
dig www.shopify.com A +short
# Returns Cloudflare Anycast IPs like 104.16.x.x
# Query from a specific DNS server
dig @8.8.8.8 example.com A +short
# Multiple A records (round-robin)
dig loadbalanced.example.com A +short
# 192.0.2.1
# 192.0.2.2
# 192.0.2.3Related CDN concepts include:
- Anycast — A routing technique where the same IP address is announced from multiple locations worldwide. The …
- CNAME — A DNS record type that maps one domain name to another (an alias). CDNs use …
- DNS (Domain Name System) (DNS) — The internet's phone book—translates human-readable domain names (example.com) into IP addresses (93.184.216.34). Every CDN request …
- TTL (Time To Live) (TTL) — How long a cached response is considered fresh before it must be revalidated or re-fetched. …
- AAAA Record — A DNS record type that maps a hostname to an IPv6 address (128-bit). The IPv6 …