A fully-qualified domain name (FQDN) sometimes also referred to as an absolute domain name, is a domain or portion of an Internet Uniform Resource Locator (URL) like http://www.lowstuff.com/fully-qualified-domain-name-facts it fully identifies the server program that an Internet request is addressed to. It specifies all domain levels, includes the second-level domain name like lowstuff.com and any other levels www.lowstuff.com. The prefix “http://” added to the fully-qualified domain name completes the URL.
Here quickly are 7 facts about fully qualified domain name you shouldn’t forget as a Network Administrator, Web Master or an internet geek.
- Every network device has a fully qualified domain name
- A fully qualified domain name always end with a period or dot (.)
- A fully qualified domain name have 3 parts: Host, domain, top level domain (.tld)
- Elements that make up a fully qualified domain name are separated by a period or dot (.)
- Fully qualified domain name (FQDN) specifies exact location of nodes in the tree hierarchy of the Domain Name System (DNS)
- Fully qualified domain name (FQDN) is always unique and unambiguous
- DNS maintains the information about the mapping between hosts’ Fully Qualified Domain Names (FQDNs) and IP addresses assigned to the hosts
1. Every network device has a fully qualified domain name:
Computers are also named to distinguish one machine from another and to allow for proper network communication.
Computers need unique addresses to talk to each other. The hostname is usually a simple string of alphanumeric characters and hyphen, the hostname means a Fully Qualified Domain Name (FQDN) that absolutely and uniquely identifies every computer hooked up to the Internet via the Domain name server (DNS) naming hierarchy.
Actually computers communicate on a network using a set of numbers with a protocol called TCP/IP which follows a specific set of rules to assure its uniqueness and validity i.e. 192.168.1.1 used for most router IP.
2. A fully qualified domain name always end with a period or dot (.)
Technically a domain is not considered fully qualified without a trailing dot, for example browsers are smart enough to put a dot at end of URL when you type an URL while requesting for pages from a server resources. Try this. Type www.lowstuff.com. The browser will still open the page as well as when you type www.lowstuff.com with a trailing dot (.) period
Name servers must be FQDNs and typically use the naming convention “ns1.example.com.” and “ns2.example.com.” So when you look up the name server on you DNS dashboard you see the trailing dot (.)
3. A fully qualified domain name have 3 parts: Host, domain, top level domain (.tld)
Your hostname is the name of your computer. Your fully qualified domain name is your hostname plus the domain
your company i.e. name of server your company uses, often ending in .local.
So if the name of your computer is goodstuff, and your company’s domain is amber.localhost, your computer’s fully qualified domain name (FQDN) is goodstuff.amber.localhost.:
- Hostname: goodstuff
- Domain: amber.localhost
- FQDN: goodstuff.amber.localhost
In the case of a domain like contoso.local I did not use an “external” internet domain name. This name doesn’t have to be the only way that you address the server.
If you make it available by its IP address you can use Domain name server or that IP address to allow external users to access it.
4. Elements that make up a fully qualified domain name are separated by a period or dot (.)
A FQDN has hostname, domain and top level domain for example for mail, ftp, store, support, etc. we would state the FQDN as mail.lowstuff.com. ftp.lowstuff.com. store.lowstuff.com.
All separated by dot (.)
5. Fully qualified domain name (FQDN) specifies exact location of nodes in the tree hierarchy of the Domain Name System (DNS)
It pinpoints the exact location in the tree hierarchy of the Domain Name System (DNS). Thus, it specifies all domain levels, including the top-level domain and the root zone.
Usually you’d have a private DNS that has your .local domain setup in it and a separate DNS server for the public where your .com lives. You don’t want to put your .local domain on a public DNS server because someone will have a way to get a list of all your hosts and it exposes your network to attack.
A FQDN always starts with a host name and continues all the way up to the top-level domain name, Essentially any activity that transfers info across a network involves the Domain Name System -DNS. If you’re connecting to a File Transfer Protocol (FTP) server or an email server, you will need to know its Fully Qualified Domain Name or IP.
If you are using only the hostname (without the domain information) to connect to a server, the application you’re using may not be able to resolve the hostname. Also, if you are trying to connect to a remote host that is not local to your Internet service provider (ISP), you will probably have to use the FQDN.
6. Fully qualified domain name (FQDN) is always unique and unambiguous
The FQDN always instructs the person or software interpreting the name to start at the root and then follow the sequence of domain labels from right to left, going top to bottom within the tree.
To name any node in the DNS name hierarchy. We simply start at the root node and follow the sequence of subdomains down to the node in question, listing each level’s labels separated by a dot. When we do this, we get single name that uniquely identifies a particular device.
Sometimes the partially qualified domain name is used to refer to network devices
There are also some situations in which we may refer to a device using an incomplete name specification. This is called a partially-qualified domain name (PQDN), which means that the name only partially specifies the location of the device.
Thus, one can only use a PQDN within the context of a particular parent domain, whose absolute domain name is known. We can then find the FQDN of a partially-specified domain name by appending the partial name to the absolute name of the parent domain.
7. DNS maintains the information about the mapping between hosts’ Fully Qualified Domain Names (FQDNs) and IP addresses assigned to the hosts
Whenever the DNS software sees a FQDN it will look up the corresponding IP address from the domain name server.
How do I find the fully qualified domain name of my computer?
To find the FQDN
- On the Windows Taskbar, click Start > Programs > Administrative Tools > Active Directory Domains and Trusts.
- In the left pane of the Active Directory Domains and Trusts dialog box, look under Active Directory Domains and Trusts. The FQDN for the computer or computers is listed.
How do you look up a Fully Qualified Domain Name?
Looking up the FQDN of your computer or server is simple. Just follow the instructions for your operating system below. If your machine does not provide the FQDN, it is not connected to a domain.
Windows 10. Within the taskbar’s “Search Windows” box, type “control panel” and select “system and security.” Next, select “system” and the FQDN is listed next to the Full Computer Name label.
Mac OS. Open terminal, and enter “hostname -f” into the prompt. Terminal will return the FQDN.
Linux. Open terminal and enter “hostname -A” into the prompt. The “A” is case sensitive. Terminal will return the FQDN.
Once you know your Fully Qualified Domain Name, you can make your device available online through the DNS.
- Begin in the Start menu
- Right-click Computer
- Click Properties
- The fully qualified domain name appears next to Full computer name
- Begin in the home screen
- Type Computer
- Right-click Computer from the search results
- Click Properties on the bottom of the screen
- The fully qualified domain name appears next to Full computer name
- Begin on the desktop.
- Type Control Panel in the “Search Windows” box in the taskbar.
- Click on System and Security.
- Click on System.
- The fully qualified domain name applers next to Full Computer Name.
The fully qualified computer name can be determined by combining the Computer Account with the Active Directory Domain from the procedure below.
- Open a terminal prompt
- Enter dsconfigad -show
- If you are connected to a domain, you will see a printout containing Computer Account and Active Directory Domain
- If you are not connected to a domain, nothing will display and your machine does not have a fully qualified domain name
- Start on the desktop.
- Open a Terminal.
- Type hostname -A (The “A” must be captialized).
- The Fully Qualified Domain Name will be given.
Sources: Sematec , labtestproject.com