DNS — how names become IP addresses — Networking & Hosting — How a Website Works, End to End

3. DNS — how names become IP addresses

Basic★ Must knowLesson 3 of 12

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Browser → OS resolver → Recursive resolver (ISP / 8.8.8.8 / 1.1.1.1)
              → Root server ("ask .com")
              → .com TLD server ("ask ns1.shop.com")
              → Authoritative server for shop.com → "www.shop.com = 20.43.10.5, TTL 300"
Answer cached at each level for TTL seconds

Record	Purpose	Example
A / AAAA	Name → IPv4 / IPv6	`www → 20.43.10.5`
CNAME	Alias to another name	`www → shop.azurewebsites.net`
MX	Mail servers	`shop.com → mail.protection.outlook.com`
TXT	Text — domain verification, SPF/DKIM/DMARC for email	`v=spf1 include:...`
NS	Which servers are authoritative	`ns1.cloudflare.com`
ALIAS/ANAME	CNAME-like at the root domain (provider feature)	`shop.com → CDN`

TTL (time to live) — how long resolvers cache the answer. Lower it (e.g. 300 s) before migrating a site so the change propagates quickly. "DNS propagation" = waiting for old cached answers to expire.

bash

nslookup www.shop.com
dig +trace www.shop.com        # see each step from the root
ipconfig /flushdns             # clear Windows DNS cache