Explain the purpose and working of DNS
This question covers the Domain Name System, a critical infrastructure component translating human-readable names to IP addresses. It tests fundamental networking knowledge.
Why Interviewers Ask This
DNS is ubiquitous in every internet interaction. Interviewers check if you understand the resolution hierarchy and caching mechanisms. This knowledge is vital for troubleshooting connectivity issues and optimizing application performance.
How to Answer This Question
Define DNS as a directory service mapping domains to IPs. Describe the hierarchical structure: root, TLD, authoritative servers. Explain recursive vs iterative queries. Mention caching to reduce load. Discuss record types like A, AAAA, CNAME. Briefly touch on DNSSEC for security.
Key Points to Cover
- Name-to-IP translation
- Hierarchical server structure
- Recursive vs iterative queries
- Caching mechanisms
Sample Answer
DNS translates domain names like flipkart.com into IP addresses so browsers can locate servers. It operates hierarchically with root servers, top-level domain servers, and authoritative name servers. When a user requests a site, a recursive resolver queries these servers iteratively until the IP is found. Caching at various levels speeds up subsequent lookups. Different record types store specific data, such as A records for IPv4 and CNAME for aliases. DNSSEC adds digital signatures to prevent cache poisoning.
Common Mistakes to Avoid
- Confusing DNS with DHCP
- Omitting record types
- Ignoring caching benefits
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