Top-level domain

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

A top-level domain is a domain directly beneath the DNS root, such as com, net, or org.

A top-level domain (TLD) is a domain directly beneath the DNS root domain, represented by a single dot. Common examples include com, net, and org. section 3.1.3 section 3.3

DNS organizes names as a tree: the root contains TLDs, each TLD contains second-level domains such as google under com, and those domains can contain further subdomains. section 3.1.3

Use these relationships to read a DNS name:

• com is the TLD in google.com. section 3.1.3
• google is a second-level domain beneath the com TLD. section 3.1.3
• www in www.google.com is a lower-level name, not a TLD; www is a conventional server name rather than a technical requirement. section 3.1.3

Figure 3.3 The DNS hierarchy. All domains are under the root domain, represented by “.”. Under the root domain, there are various top-level domains. Under each top-level domain, there are various second-level domains. The “google” domain, a subtree under the “com” top-level domain, is highlighted.

The hierarchy diagram places the root above TLDs and highlights google as a subtree beneath com. section 3.1.3

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes

Explains placement beneath the root and above second-level domains, but does not detail TLD server operation.

Examples

Uses com, net, org, and google.com to illustrate TLD placement.

What you can do after

Evaluate a domain name’s position in the DNS hierarchy and distinguish its TLD from its second-level domain.

How it connects

Connects the root domain, second-level domains, subdomains, and fully qualified domain names.

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Related concepts

• root domainpart of · A root domain is the highest-level domain in a domain-name hierarchy, from which subordinate domains are organized.
• second-level domainhas part · A second-level domain is a domain directly beneath a top-level domain, such as google beneath com.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.