DNS Propagation Delay
DNS propagation delay occurs when DNS record changes have not yet spread across all DNS resolvers worldwide. Changes to A, CNAME, MX, or NS records are cached by resolvers according to the TTL (Time to Live) value, meaning updates may not be visible everywhere immediately. Propagation typically takes 1–48 hours depending on TTL configuration and resolver behavior.
Symptoms
- Website resolves to old IP for some users but not others
- Email delivery fails intermittently after MX record changes
- New subdomain works from some locations but returns NXDOMAIN from others
- SSL certificate validation fails because CAA/DNS records haven't propagated
Common Causes
- High TTL values on the old DNS records (e.g., 86400 seconds = 24 hours)
- ISP resolvers caching records longer than the specified TTL
- Authoritative nameserver not returning updated records consistently
- Negative caching of NXDOMAIN responses for new records
Step-by-Step Troubleshooting
- 1
Check current DNS records
Use a DNS lookup tool to verify what records are currently published on the authoritative nameserver.
Use DNS Lookup → - 2
Compare records from multiple resolvers
Check DNS records from different resolvers (Google 8.8.8.8, Cloudflare 1.1.1.1) to see if propagation is complete.
Use DNS Lookup → - 3
Check SOA record for TTL values
The SOA record contains the minimum TTL and refresh intervals. High values will slow propagation.
Use SOA Record Lookup → - 4
Lower TTL before making changes
Before future DNS changes, reduce TTL to 300 seconds (5 minutes) at least 24 hours before the planned change.
- 5
Flush local DNS cache
Clear your local DNS cache (ipconfig /flushdns on Windows, sudo dscacheutil -flushcache on macOS) to see updated records.
- 6
Set up DNS monitoring
Monitor DNS records continuously to get alerts when changes propagate or when unexpected modifications occur.
Recommended Diagnostic Tools
Monitor DNS Propagation
Get real-time alerts when DNS records change or propagation completes.