Definition of FQDN in The Network Encyclopedia.
What is FQDN (fully qualified domain name)?
FQDN stands for Fully Qualified Domain Name. In the Domain Name System (DNS), FQDN is a dotted name that fully identifies a TCP/IP host on the Internet. A fully qualified domain name (FQDN) of a host consists of its host name dotted together with its domain name and any names of subdomains in which the host resides.

FQDNs are used in Uniform Resource Locators (URLs) for accessing Web pages on the Internet and provide an absolute path through the DNS namespace to the target host on which the Web page resides. They are also sometimes called absolute domain names.
Example of a FQDN
For the FQDN server12.networkencyclopedia.com, the TCP/IP hostname is server12 and its domain is networkencyclopedia.com.
External References
- RFC 1035 – Domain Names – Implementation and Specification, November 1987
- RFC 4703 – Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients, October 2006
- RFC 4702 – The Dynamic Host Configuration Protocol (DHCP) Client Fully Qualified Domain Name (FQDN) Option, October 2006