To analyze domain resolution issues systematically, you can follow these steps and methods. These steps will help you identify the root cause and find a solution effectively:

Domain Resolution Issue Analysis Method

1. Verify Basic Information

• Ensure the domain name is spelled correctly.
• Check if the domain is registered and within its validity period.
• Confirm that DNS records (e.g., A records, CNAME, etc.) are correctly configured on the domain management platform.

1. Check Domain Resolution Using DNS Query Tools

• Command Line Tools: nslookup or dig
  • Run the command nslookup yourdomain.com or dig yourdomain.com to check the DNS resolution results.
  • Verify if the returned IP address matches the expected IP address.
• Check whether there are any resolution records (such as A records, CNAME records, etc.). If there are none, the DNS records may not have taken effect or may be misconfigured.

1. Check DNS Server Configuration

• Ensure the local DNS server is functioning properly. If you’re using an ISP’s DNS server, there may be caching or delay issues.
• Switch to public DNS servers (e.g., Google DNS: 8.8.8.8 and 8.8.4.4 or Cloudflare DNS: 1.1.1.1) and then test the domain resolution again.
  • Example command: nslookup yourdomain.com 8.8.8.8 (specifying Google’s DNS server for the query).

1. Clear Local DNS Cache

• On Windows, you can clear the local DNS cache by running:
  ipconfig /flushdns
• On macOS, use:
  sudo killall -HUP mDNSResponder
• On Linux, use (depending on the DNS service):
  sudo systemd-resolve --flush-caches

1. Verify if DNS Records Have Propagated

• Use online tools (such as whatsmydns.net) to check the global resolution status of the domain. This allows you to verify if the DNS records have propagated in various regions.
• If certain regions haven’t resolved the DNS, it may be due to DNS propagation delay, and you might need to wait a bit longer.

1. Check Domain and Server Status

• Log in to your domain management platform to ensure the domain is marked as “Active” or “Valid” and has not been suspended, locked, or expired.
• Confirm that the domain’s DNS server settings are correct. If using custom DNS servers, ensure they are valid and can correctly resolve the domain.

1. Check Server and Firewall Settings

• Ensure that the target server (e.g., 128.204.223.119) is online and can respond to requests properly.
• Review the server’s firewall configuration to ensure it allows requests from different DNS queries.
• If the server has firewall rules that restrict certain IP addresses or ports, it might affect domain resolution and access.

1. Contact Domain Registrar or DNS Service Provider

• If the above steps do not resolve the issue, contact the domain registrar or DNS service provider’s technical support. They can check the backend configuration of the domain and help resolve the issue.

Common Commands Summary

Tool	Command	Description
nslookup	nslookup domain.com	Query the DNS resolution for a domain
dig	dig domain.com	Get detailed DNS information for a domain
ipconfig	ipconfig /flushdns	Clear the DNS cache on Windows
ping	ping domain.com	Test if the domain can be accessed
traceroute / tracert	tracert domain.com	Trace the route path and check network latency