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Web & Networking Foundations · Foundational networking

How Networks Work, Part 2: DNS, TLS, and Certificate Trust

Learn how DNS resolves hostnames and how TLS uses certificates to provide confidentiality, integrity, and server authentication.

Before we begin, here is exactly what you will be able to do by the end of this lesson.

By the end of this lesson, you will be able to:

  • Describe how a domain name is structured as a right-to-left hierarchy and trace how a DNS lookup travels from your resolver through the root and authoritative servers.
  • Explain why DNS answers are cached and what a TTL (time to live) controls.
  • Identify the common DNS record types — A, AAAA, CNAME, MX, TXT, and NS — and state what each one provides.
  • State the three guarantees TLS provides (confidentiality, integrity, and server authentication) and explain why the padlock does not mean the application behind it is secure.
  • Describe how a server's certificate chains up to a trusted Certificate Authority to form the chain of trust the browser uses to accept it silently.
  • Use nslookup or dig to look up DNS records and read a live certificate in the browser, identifying the issuer, validity dates, and covered hostnames.

When you are ready, send Continue.