DNS Propagation Delay
Overview
DNS propagation refers to the time required for DNS record changes to update across global DNS resolver caches. When DNS records are modified, recursive resolvers may continue serving cached records until their time-to-live (TTL) expires. During this period, users may resolve different IP addresses depending on their resolver.
Common Causes
- high TTL values on DNS records
- recent changes to A, CNAME, or MX records
- switching hosting providers or server IP addresses
- updating nameservers at the domain registrar
- DNS caching by local networks or internet service providers
How the Problem Appears
- some visitors seeing the new website while others see the old server
- inconsistent DNS lookup results between locations
- email routing still using previous mail servers
- DNS lookup tools reporting different IP addresses
How It Is Diagnosed
- running DNS queries from multiple geographic locations
- checking TTL values on existing DNS records
- using
dig domain.comto inspect current resolver responses - comparing authoritative DNS responses with cached resolver responses
Typical Fix
- reduce TTL values before planned DNS migrations
- wait for resolver caches to expire globally
- flush local DNS caches on testing machines
- confirm the authoritative DNS records are correct