Discover new features of services for free! Sign up now


DNStable classroom

In our chapters you will find interesting and important information about domains, DNS records and DNS lookup.

We wish to create a really helpful and interesting section, so we invite you to be our co-authors.

Please, send us your articles to and we will publish most interesting of them under your copyright.

Table of content

DNS stands for Domain Name System, which is the largest digital database in the world, containing information about every web site on the internet. Every web site online has an IP address that is its actual internet location, and this number is used to locate the web site within the database. The data that tells the web server how to respond to your input is known as the DNS records, or zone files. These records play a vital role in the functionality of the internet, and any aspiring internet technology expert should learn the following facts about DNS records and how they are used.
DNS Records Explained

DNS records are basically mapping files that tell the DNS server which IP address each domain is associated with, and how to handle requests sent to each domain. When someone visits a web site, a request is sent to the DNS server and then forwarded to the web server provided by a web hosting company, which contain the data contained on the site.

Various strings of letters are used as commands that dictate the actions of the DNS server, and these strings of commands are called DNS syntax. Some DNS records syntax that are commonly used in nearly all DNS record configurations are A, AAAA, CNAME, MX, PTR, NS, SOA, SRV, TXT, and NAPTR. The following paragraph details the meaning and usage of each of these syntax.

DNS Syntax Types Explained

An "A" record, which stands for "address" is the most basic type of syntax used in DNS records, indicating the actual IP address of the domain. The "AAAA" record is an IPV6 address record that maps a hostname to a 128-bit Ipv6 address. Regular DNS addresses are mapped for 32-bit IPv4 addresses. In other words, the A-record tell which IP address to send the user to for each domain or subdomain. This means that you can have different subdomains of your website pointing to different IP addresses.

The "CNAME" record stands for "canonical name" and serves to make one domain an alias of another domain. CNAME is often used to associate new subdomains with an existing domain's DNS records. This helps when running multiple services (like an FTP and a web server; each running on different ports) from a single IP address. Each service can then have its own entry in DNS (like and Network administrators also use CNAME Records when running multiple web servers on the same port, with different names, on the same physical host.

The "MX" record stands for "mail exchange" and is basically a list of mail exchange servers that are to be used for the domain. MX record is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain and a preference value used to prioritize mail delivery if multiple mail servers are available. The set of MX records of a domain name specifies how email should be routed with the Simple Mail Transfer Protocol.

The "PTR" record stands for "pointer record" and maps an Ipv4 address to the CNAME on the host. PTR records, also commonly known as reverse DNS lookup or reverse DNS resolution, maps an IP address to a host/domain name. This is the opposite of resolving a domain name to an IP address which is commonly known as the A record in IPv4 and the AAAA record in IPv6. Published Standard: RFC 2317

This record is used by spam filters. Spammers often use fake domain names to send out email and generally won't have a correct PTR record set up in DNS. This is one of the main requirements of many spam filters and if you don't have a PTR Record setup many of your emails will be blocked and never reach the intended recipient.

Generic PTR are records that look like they have a repeating, psuedo random string, or a alpha-numeric sequence. Something similar to Your PTR record should be unique and usually take on the form of "". Many spam filters run your PTR record through a series of regex's to determine if it matches a generic string. You can also read some of the different Postmaster Guidelines. You can test to see if you have a Generic PTR record, by sending an email to, which will auto-respond with the results. Keep in mind "Mailtest" will perform the test on all your MX records and IP's in your email header, but only your out-going mail servers or LSIP (Last sending IP address) needs to have a rDNS PTR record. But it's good practice to set one up for all of them.

The "NS" record stands for "name server" and indicates which Name Server is authoritative for the domain.

An "SOA" record stands for "State of Authority" and is easily one of the most essential DSN records because it stores important information like when the domain was last updated and much more.

An "SRV" record stands for "service" and is used to define a TCP service on which the domain operates.

A "TXT/SPF" record lets the administrator insert any text they'd like into the DNS record, and it is often used for denoting facts about the domain. An SPF Record, or Sender Policy Framework (SPF), as defined in Experimental Specification RFC 4408, is an email validation system designed to prevent email spam by tackling source address spoofing, a common vulnerability. SPF allows administrators to specify which hosts are allowed to send email from a given domain by creating a specific SPF record in the public Domain Name System (DNS). Mail exchangers then use the DNS to check that mail from a given domain is being sent by a host sanctioned by that domain's administrators.


DNS records are an important, yet unseen aspect of how the internet works. If you're studying internet technology or training to become a server administrator, you will definitely need to learn more information about all of the aforementioned DNS record types and their uses.

Read more...Hide

Most people understand that a domain name is simply the basic web address of a web site, but few people actually understand how domain names work. If you're struggling to understand the basics of how domain names function on a technical level, then the information contained herein may prove to be quite useful.
A domain name is actually a lingual representation of an IP address, which is a series of numbers separated by dots. Every web site is given an IP address, however it is much more difficult to remember this segmented sequence of numbers instead of remembering a simple phrase. This is the basic concept of domain names, but the process through which an IP address is translated into a domain names is a bit more complicated.

Domain Name Levels

Domain names are divided into three different levels that represent different parts of a domain name. The first level (also known as the top-level) of the domain is the extension of the domain. For example, in the domain name "," the .com portion of the domain is the top-level domain (TLD).

There are also country code top-level domains that are referred to as ccTLDs.

In all, there are over 200 top-level domains (TLDs) or domain name extensions to choose from, most of which are country code TLDs. Generic TLDs contain three or four letters, like .com, .net, .org, or .info, while country code top-level domains usually contain two letters following a .co, such as (United Kingdom) or (India). A complete list of country code TLDs can be found on the official IANA web site.

Domain Name Formatting

Domain names have to be at least two characters long and cannot exceed 63 characters total (minus the TLD). Domain names can include any combinations of numbers, letters and hyphens, but cannot contain any other symbols or spaces. The first and last characters of a domain name cannot be a hyphen.

Connecting Domain Names to IP Addresses

When you type in a domain name in the address bar of your browser, you're actually connecting to a specific IP address. The domain name is directly associated with this IP address upon registration, and the connection of domain names to IP addresses is managed and regulated by ICANN ( Internet Corporation for Assigned Names and Numbers).

The best analogy for domain names and IP addresses would be vanity phone numbers – you can call some numbers by inputting a word or phrase into the keypad of the phone, but in reality, you're actually accessing a phone number through your telephone line. Technically, you can enter the IP address of a web site into your browser and it will appear as usual, but this is rarely done because it is much less convenient.

Domain Name Registration

In order to associate a domain name with a web site or an IP address, you must first register the domain (by purchasing it). Registering a domain name is simple and requires no special skills or prerequisites. ICANN continuously maintains a list of accredited domain registrars from which you can purchase domain names. Domains are registered for a specified time period, after which the domain expires and is open for new registration by another individual or business. When a domain registration is about to expire, the registrant of the domain is notified via email or phone call within two weeks of the expiration date.

It is important to note that intellectual property rights do apply to domain names, so you are not legally allowed to register a domain name that contains a term or phrase that is trademarked or copyrighted.

Pointing a Domain Name

After registering a domain name, it is necessary to point the domain name to a web site. This can usually be done within the control panel of the domain registrar's web site. Simply change the name servers of your domain, and it will be pointed towards whichever nameserver you'd like.

Usually, you will need to obtain the names of these nameservers from your web hosting company. Most web hosts will include information on how to point your domain in the proper fashion. It is important to note that it can take anywhere from a couple of minutes to several days for a domain to become active on the internet after the official completion of registration and nameserver adjustments.

Read more...Hide

Domain names are an integral part of the way the internet functions, as they directly represent the name of a web site. Without domain names, a web surfer would have to type in an IP address in the address bar of their browser, which is basically a string of numbers separated by dots.
Obviously, these segmented number sequences are much more difficult to remember than the standard web site name, thus domain names were invented.

Understanding the basics of domain names is rather simple, especially for those with adequate internet knowledge and a bit of technical sense. However, trying to judge the value of a domain name is much more difficult. In fact, there are even companies and individuals known as domain speculators that specialize in judging the value of domain names. There are three basic factors that directly contribute to the value of a domain name: memorability, keyword/SEO optimization potential, and the value of the attached site (if applicable). If you're curious about the value of a domain name, then you may find the following information to be quite useful.

The Length of the Name

Statistically, domain names that are shorter have been sold for higher profits. This is because shorter domain names are generally more memorable, and therefore, they become popular more easily than longer domain names. The length of the domain name is the most important factor that affects the memorability of the attached web site. In addition, with a shorter domain name, there is a lessened likelihood of typos.

In today's competitive internet industry, it is nearly impossible to find a domain name that is shorter than six letters. Names like eBay, Ask, Google, Yahoo, Go, and Bing are all perfect example of incredibly popular domain names that are under six letters. Purchasing a domain name that is less than six letters usually requires you to bid on the name at an auction site, or purchase the domain directly from the owner. Either way, these domains are never cheap, and they are usually more than $10,000.

Keyword/SEO Optimization

Another very important factor to consider when judging the value of a domain name is whether or not the name contains and frequently searched for keywords. For example, although the word "basketball" is much more than six letters, it is a very common term that would most likely yield a lot of web traffic from search engines.

When people purchase domain names, ideally they'd like to put forth minimal effort to begin seeing progress. For this reason, many domain speculators and webmasters only buy domain names that already have a significant keyword value. Thus, it is important to consider the predefined popularity of name before judging its value. For example, while the domain name "" may sound appealing to some people, it has no keyword value because nobody is searching for that term. When registering domain names, it is best to ensure that your desired name has some inherent keyword value.


Although the term "commerciality" is not technically a word in the dictionary, it is commonly used in the internet industry to describe something with commercial value. If the domain name pertains to something that can be sold or marketed, then there is a very high chance that it will sell for a greater price. A domain name that is related to a popular product would be much more valuable than a domain name that is simply related to a funny phrase or a personal opinion, even if the "non-commercial" domain is shorter. The more of an opportunity there is to make a profit with the domain, the more likely someone will make a substantial investment to acquire the domain.

Letters and Numbers

Surprisingly, even though domains that contain hyphens and numbers are often more appealing and easier to read, these domain names generally rank lower in the search engines. Most people do not include numbers or hyphens when they submit a search engine query. Thus, most domain speculators recommend purchasing a domain name that does not contain any hyphens (-) or numbers.

Many people make the mistake of purchasing a domain name like "" simply because the alternative "" is not available. If you run into a roadblock like this, it may be best to move in to a new idea, rather than purchasing a domain name with hyphens and/or numbers. Choosing a domain name that is memorable, contains no symbols or numbers, and includes popular keyword phrases is the best way to ensure that your domain name investment is safe and profitable.

Read more...Hide

The domain name system, also referred to as simply the DNS, is an intricate worldwide network of web servers that collectively comprise a global database of domain names and IP addresses. The domain name system is the central point of the entire internet, and it is directly responsible for the way web addresses are used.
The job the domain name system is to take standard web addresses and domain names and translate them into segments of numbers that are compatible with computer dialogue. These numbers are known as IP addresses, and they are an integral part of the way the internet works.

Domain Name System and Domains

The domain name system is organized into a carefully structured hierarchy of servers that transmit data, keep the DNS database secure, and ensure its continuity. When you register a web site, the site that you used to purchase your domain name usually holds the DNS records for your domain. DNS servers are also referred to as simply "nameservers." Domains are stored on the DNS servers to which they are "pointed." Pointing a domain is as simple as changing a setting within the control panel of your domain registrar account.

Assigning DNS Servers

The owner of a domain has the right to point their domain towards any DNS they would like, and after purchasing a hosting plan, a domain owner will usually point their domain towards the DNS of their web server. Pointing a domain is as simple as typing the web address of the DNS server into a box. A DNS server web address usually appears as NS1.WEBHOST.COM and NS2.WEBHOST.COM. Every web host has two nameservers for redundancy, or protection from any unexpected mishaps, such as server crashes and security attacks. Although nameserver addresses are frequently displayed in capital letters, they are not case sensitive.

Finding the address of your web hosts nameserver is as simple as asking a hosting agent or browsing the control panel of your hosting account. Most of the time, this information will be displayed within the control panel of your web hosting account.

How IP Addresses Are Loaded

IP addresses are managed by different organizations that independently own DNS servers. For example, all .com web addresses are handled by Network Solutions, Inc. Thus, when a .com web site is accessed in your web browser, the site is loaded from a DNS server at Network Solutions, Inc., and the data is then transferred to your computer based on the URL that is attached to the IP address. Most people don't realize that they can also enter in the exact IP address of the site instead of the domain name and access the same information.

In essence, the domain name system is simply a database that translates regular letters into numbers that computers can decipher and use for communication. The database is distributed evenly amongst thousands of servers to prevent data failure, ensuring that every web site remains active and can be accessed when entered into the address bar of a browser.

Read more...Hide

A DNS (Domain Name System) server is a type of web server used to interact with the domain name system, which is the global directory of domain names and corresponding IP addresses. DNS technology automatically translates long and confusing IP address (which are segmented number sequences separated by dots, such as into standard domain names that are easier to remember.
The domain name system is comprised of thousands of domain name servers around the world, which accumulatively make up the largest digital database on the planet. DNS servers operate using special software that transmits data from the DNS server to various web hosts upon request. In basic terms, the internet would fail to exist as we know it without the Domain Name System and DNS servers.

What is a DNS Root Server?

DNS root servers are the base of the domain name system, communicating only with each other using private network encryption protocols. These web servers are at the top of the internet hierarchy, storing all information related to a domain name and its IP address. There are only 13 root servers in the entire world, each one labeled a letter of the alphabet, up to M. Ten of these crucial servers are located within the United States, with one in London, one in Japan, and one in Sweden.

What is the DNS Hierarchy?

The domain name system is operated in a hierarchy that keeps the domain name database separate, and the only servers that house the entire database are the aforementioned DNS root servers. The rest of the DNS servers in the world house only fragments of the database for particular web hosts and web sites. Most of these low level DNS servers are owned by Internet Service Providers or private businesses.

When you browse a web site, your web browser is actually directly communicating with your ISP's DNS server to retrieve data from other domains before displaying it on your screen. In some cases, the DNS server will not need to communicate with another server to display the page; however, in many cases, especially when you visit a foreign or private web page, your ISP's DNS server will have to act as a DNS client and retrieve data from another DNS server.

Your Connection to DNS Servers

Every computer that is connected to the internet is also connected to a DNS server. When you setup a connection through your Internet Service provider, you are actually establishing a connection with their DNS server. You are given a public IP address that is used to identify your computer on the network.

If you are a webmaster, then you will need to learn the web address of your web host's DNS server in order to point your domain to that server. Doing this is usually as simple as typing the web of the DNS in your domain registrar’s control panel.

Read more...Hide

A TLD (top-level domain), also referred to as a domain extension, is simply the letters that appear at the end of a domain name. For example, in the domain name "," .com would be the TLD.
All of us are familiar with .com, and most internet savvy individuals are aware of its intended uses, being that it is an abbreviation for commercial. However, there are many other types of TLDs assigned by the IANA (Internet Assigned Numbers Authority) that are commonly used, and many many people are not familiar with their meaning or their usage.

If you're interested in learning more about common TLDs and their uses, the following information may be useful.

Most Common TLDs

At the moment, there are 20 different TLDs available that are not country codes, including some less conventional and seldom mentioned ones like .aero. The following list depicts some of the most popular TLDs and their intended uses.

  • .com (commercial) – The most popular TLD, .com was meant to be used for commercial purposes, but is now used for virtually every cause imaginable.
  • .net (network) – Intended for network web sites, this TLD is also commonly misused for a variety of purposes.
  • .org (organization) – Another commonly misused TLD, .org was originally meant for sites that represent organizations and non-profits.
  • .edu (education) – This is usually used by colleges and other educational institutions, and it is not typically available for public registration.
  • .mil (military) – Restricted to military use only, .mil is not available for public registration.
  • .gov (government) – Restricted to government use only, .gov is not available for public registration.
  • .co (company) – A newly launched TLD, .co is speculated to become popular and a runner-up alternative to .com.
  • .biz (business) – This is one of the rarer TLDs on the list. .biz is intended for business use, but its popularity pales in comparison to the .com TLD.
  • .info (informational) – This TLD has gained a lot of popularity because, surprisingly, it has the potential to rank highly in the search engines, even though registration only costs about a dollar.
  • .me (personal) – The least common on this list, .me is often used for personal websites.
  • Uncommon Facts About TLDs

    Since .com, .org and .net tend to have higher search engine rankings, these are the most popular and misused TLDs. Aside from .me and .info, most of the common TLDs contain three letters, however one of the most important TLDs on the internet that is seldom mentioned is .arpa. ARPA stands for Address and Routing Parameter Area, and this is the TLD used to maintain the integrity of the internet. Most .ARPA domains are designated to domain servers that maintain the domain database of the internet.

    Country Code TLDs

    Unlike conventional TLDs, country code specific TLDs contain two letters following a .co. For example, the country code TLD for the United Kingdom is The popularity and prevalence of country code domains depends upon that particular part of the world because search engines return geo-targeted results.

    While the above list contains only nine of the most common global TLDs, there are approximately 200 country specific TLDs available for registry at the moment. The new .co domains were originally intended to represent sites in Columbia, but has now been transferred to global commercial use and is being marketed as an alternative to .com by some registrars.

    Read more...Hide

    DNS stands for domain name system, which is the database responsible for storing all of the information pertaining to IP addresses and domain names online. DNS servers are used to carry and transmit this data from one computer to another.
    All of this data is stored on a network that is backed up by thousands of separate DNS servers and stored on single root DNS servers in the United States, Japan, London and Sweden.

    These servers carry tremendous volumes of data, and every day, the network is growing. Fortunately, there is a way to conduct a DNS lookup to obtain some of this data for whatever reason you see fit. The following information outlines the process of conducting a DNS lookup and some of the reasons why people usually use DNS lookup services.

    WHOIS Database

    The database previously mentioned that stores all of the DNS records of the world is called the WHOis database and can be searched through several different web sites. The main site for WHOIS lookups is Network Solutions, Inc.'s site (a company that is partially responsible for maintaining the records). is also commonly used to obtain domain registration details and DNS records.

    Unfortunately, there is no way to verify whether the information you find in the WHOis database is accurate or truthful, as there are no requirements for providing authentication of data when registering a domain name. In other words, anyone can register practically any site they would like in any name, with any address, with the exception of government or military sites. Nonetheless, many times, the WHOis database will return enough information to proceed with your investigation.

    Preventing Spam

    One of the reasons why people use the WHOis database to look up information is to prevent spam attacks from a particular web server or IP address. When your site is attacked by spam repeatedly, it is possible to obtain the IP address(es) of the attackers and then use a reverse DNS lookup tool to obtain site registration information of that IP address (if there is any).

    It is important to note that these reverse lookup tools differ from the conventional WHOis searches because you are obtaining information based on the IP address, instead of an actual domain name. It may be very difficult to obtain the identity of the spammer, but it is possible to contact their web host and have them shut down if the right information is obtained from the reverse lookup service.

    Maintaining Site Security

    Even more violent than spam is the dreaded DDoS attack , which is basically a security attack on your web site from dozens or even hundreds of IP address simultaneously. The DDoS (Distributed Denial of Service) attack in particular is geared towards causing your server to crash due to an overload of fake traffic in a short period of time. However, some hackers will use the same method to guess your site's passwords by repeatedly sending requests until the correct password is retrieved.

    If you notice an unusual amount of traffic suddenly, then you may want to conduct a reverse DNS lookup and get to the root of it before it becomes a problem, especially if the traffic is originating from a group of similar IP addresses.

    Read more...Hide

    The DNS (Domain Name System) is a massive network of servers that comprises the largest digital database on the planet. This database is maintained, managed and regulated by several internet authorities, including the IANA (Internet Assigned Numbers Authority) and ICANN (Internet Corporation for Assigned Names and Numbers).
    Many people confuse the various terms associated with the DNS and mistakenly refer to them as either the same thing or completely separate entities. In truth, they are neither separate nor are they the same thing; rather, they are integral pieces to the puzzle that is the world wide web.

    If you're interested in learning the difference between a DNS and a name server, then you may want to consider the following information.

    What is the DNS?

    Contrary to a seemingly popular misconception, DNS does not stand for Domain Name Server or Domain Name Software. DNS is an abbreviation for the aforementioned system that catalogs every domain and IP address on the internet, including registration information, as well as their relation to other domains and web hosts. The DNS is the central database of the internet, and without it, the internet would cease to exist as we know it.

    Before the domain name system was devised, computers would connect to each other via IP addresses, which are strings of segmented numbers separated by dots. An example of an IP address would be (a common IP address for a local router). The domain name system attaches a name to this number so that site visitors can easily remember and return to web addresses.

    What is DNS Software?

    DNS software is a program that is installed on a web server and used to facilitate the transference of data related to the domain name system. Technically, any web server can have DNS software installed on it, making the server a name server; however, some web hosts will not allow you to install or configure software within your hosting control panel, especially in shared hosting plans. If you're interested in installing DNS software on a web server to create a custom nameserver, you'll either need a VPS or dedicated hosting plan, unless you'd like to invest several thousand dollars in a private web server.

    What is a Name Server?

    A name server is a web server that has DNS software installed on it, particularly a server that is managed by a web host that is specifically designated for managing the domain names that are associated with all of the hosting provider's accounts. Name servers are often called DSN servers as well, and this is likely the origin of all of the confusion associated with name servers and the DNS.

    Every web site has two name servers to which it is pointed, and this process must be done by the webmaster upon purchasing a domain and a hosting account. If you have more questions about domain name pointing and your web hosting name servers, it is recommended that you contact your web hosting provider.

    Read more...Hide

    Having a web site with a popular name is a great way to gather residual web traffic with minimal effort. Unfortunately, most people don't realize that they can double this effect through the practice of domain forwarding, which is a grossly underused and highly effective tactic that has many uses.
    Domain forwarding is also known as URL forwarding. It is a practice often utilized by advanced webmasters, but can be easily done by anyone with a web hosting account, a web site and basic technical knowledge. The following information outlines the process of using domain forwarding, including how it is done and what benefits it provides for certain situations.

    Changing the Name

    Most people are quick to choose the name of their first web address because they are excited to begin their endeavors on the world wide web. Unfortunately, after the name has been chosen, there is no way to change it, so you'll have to live with it forever unless you buy a new domain name, or so is the common misconception. Obviously, the best way to avoid this would be to be very careful when selecting a domain name for your site. After the fact, the only option left is domain forwarding.

    Some webmasters that are new to search engine optimization would simply buy a new domain name and transfer their site's pages to the new site. If the search engines have already indexed the pages on the old site, the new site will be hit with a duplicate content penalty and rank poorly after the files have been transferred over. To avoid this dire situation, you can use domain forwarding within your control panel.

    Extra Domains

    Some people purchase large volumes domain names that are related to a specific niche and do not use them for an extended period of time. After letting the domains sit for a while, they decide to utilize them, but they don't want to go through the hassle of building multiple sites. If you still want to utilize those extra domain names in your niche, you can forward them all to the main domain name and then begin advertising the extra domains across the internet.

    Domain forwarding can also be a useful tactic if the extra domains contain keywords, as it is possible to get these domains to rank highly in search engines before forwarding them by simply adding a bit of content to them and waiting a few weeks. After each domain has built up a small amount of backlinks and PR, you can then forward these domains to the main site to increase search engine traffic for a short period of time and utilize the additional domains without having to completely construct all of the sites.

    URL Redirection

    URL redirection is very similar to domain forwarding, except instead of forwarding the entire domain, you can forward a specific page on a domain to another page within the same domain. This is incredibly useful if you've recently moved content or rearranged the structure of your site. URL redirection and domain forwarding are two tactics that every webmaster should learn and utilize at some point in their career.

    Read more...Hide