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DNS Resolution Simulator

Learn how DNS works with an interactive step-by-step simulator. Visualize the DNS hierarchy, understand caching at different levels, and see the difference between recursive and iterative queries.

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DNS Resolution Simulator

Watch step-by-step how your browser resolves domain names to IP addresses

Domain
Record Type
DNS Resolution Path
Browser
OS Cache
DNS Resolver
Root Server
TLD Server
Auth Server

💡 Key Takeaways

  • DNS is hierarchical: Your query travels through multiple levels (browser → OS → resolver → root → TLD → authoritative).
  • Caching speeds things up: Each level can cache results. A cache hit avoids the full lookup chain.
  • TTL controls freshness: Records expire after their TTL. Lower TTL = fresher data, but more lookups.

Understanding DNS Resolution

DNS Hierarchy

  • Root Servers (.): The top of the DNS hierarchy. 13 root server clusters worldwide direct queries to TLD servers.
  • TLD Servers (.com, .org): Manage top-level domains and point to authoritative nameservers.
  • Authoritative Servers: Hold the actual DNS records for specific domains.
  • Recursive Resolvers: Your ISP or DNS provider (like 1.1.1.1 or 8.8.8.8) that does the lookup work.

DNS Record Types

  • A Record: Maps domain to IPv4 address (e.g., 192.168.1.1).
  • AAAA Record: Maps domain to IPv6 address (e.g., 2001:db8::1).
  • CNAME Record: Alias pointing to another domain name.
  • MX Record: Mail server for the domain.

Key concepts

  • TTL (Time To Live): How long a DNS record can be cached before needing refresh.
  • Recursive query: The resolver does all the work and returns the final answer.
  • Iterative query: Each server returns a referral; the client follows the chain.
  • DNS caching: Happens at browser, OS, and resolver levels to speed up lookups.

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