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Networking Fundamentals · Foundational

Domain Name System (DNS)

The hierarchical, distributed system that translates domain names into IP addresses and other records, using UDP and TCP port 53.

Definition

DNS consists of resolvers, root servers, top-level domain servers and authoritative servers. Queries normally use UDP 53, while zone transfers and large responses use TCP 53. Resource records include A, AAAA, CNAME, MX, NS, PTR, SOA, TXT and SRV.

Example

nslookup www.example.com returns the site's IP address.

Exam tip

DNS = port 53 UDP and TCP. "It's always DNS" when names fail but IP addresses work.

Don't confuse it with

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