What is domain name system dns. Enabling and configuring a DNS server

Many owners of home PCs, laptops and tablets use the Internet without understanding the principles of its functioning at all. You can get a much more stable connection than the provider usually provides, taking the time to study this issue. One of the possibilities to improve the comfort of using the network is to replace the default DNS address with an alternative one.

What is DNS and what is it for

First, let's figure it out: what is the meaning of the DNS letter combination. The full name is Domain Name System, and translated into Russian means "domain name service". Each site on the Internet has its own domain name, we see it every day in the address bar of the browser. For example, for the well-known social network Facebook it will look like this https://www.facebook.com. In addition, each site has its own IP address in the form of a numerical value, like this: 31.13.65.36.

DNS server translates the domain name of the site into an IP address

The function of DNS is to store information about the addresses and domain names of sites. When an alphabetic request for a site name is received, the DNS server returns the numeric value of the resource address.

How to find out which DNS is provided by your ISP

If you periodically have difficulties with accessing the Internet, it is better to use the setting of a specific DNS address, rather than automatic configuration. This connection works more stable. To do this, you need to find out the address of your provider. The easiest way is to call the operator of your Internet service provider. If this is not possible, find out the DNS address using Windows tools. To do this, you need to call the command line.

You must do the following:

1. Open the "Start" menu, then "All Programs", on the "Standard" tab, click "Command Prompt".
   

   Enter the "Start Menu" select "Command Prompt"

2. Alternative way: press the Win and R keys simultaneously - in the tab that appears, type the command "cmd" and click "OK"

   On the Run tab enter the command "cmd" and click "OK"

3. In the window that appears, enter the command "nslookup" and press "Enter".

   In the Command Prompt type "nslookup" and press "Enter"

4. This will give you the value of the provider's DNS address.

   The "Command line" window will display information about the IP address of your provider

Alternative DNS servers on the Internet, overview, pros and cons

Each ISP has its own DNS service, but sometimes it makes sense to connect to an alternate server. The reasons can be different:

• the provider is not able to provide stable DNS operation;
• the user seeks to increase the level of protection of his computer;
• the owner of the PC wants to increase the speed of the network;
• desire to get rid of restrictions on access to information based on territorial location.

Let's consider the best options and try to choose the most suitable one.

Google Public DNS

The service was launched in December 2009 as an experimental service. It is currently the largest public DNS service in the world, processing an average of over 70 billion queries per day. It uses the CDN (Content Distribution Network) information transfer method. Google Public DNS servers support the IPv6 Internet protocol.

Video: a detailed and accessible description of installing an alternative DNS from Googl

Its undeniable advantages are:

1. High speed - ensured by the use of the latest technical developments.
2. Reliability - obtained through the use of powerful servers and an extensive infrastructure.
3. Security - based on the use of proprietary software.

The only drawback is associated with the activities of the service - the collection of data about users to make money on advertising. This is not a serious security breach, but it could potentially be the disclosure of your personal information.

Open DNS

Open DNS is the largest, most reliable DNS service on the Internet. Has 12 global data centers. It uses Anycast routing technology, so it responds to DNS queries faster than other providers. Websites will load faster and you don't have to worry about DNS glitches depending on your ISP. More than 50 customizable filtering categories allow parents to control the sites their children visit. Open DNS blocks sites that try to steal your sensitive information and passwords by pretending to be legitimate sites.

Video: how to set up Open DNS on your home computer

Its advantages:

1. Fast response to requests thanks to the use of new technologies and an extensive network of servers.
2. High degree of reliability achieved through the use of the latest equipment.
3. The ability to stop an Internet attack before it occurs - the service filters traffic, it has its own database of malicious sites.
4. Basic features are provided free of charge.
5. Setting up takes literally minutes.

The disadvantage is the need to register for the service.

DNS WATCH

If you need complete confidentiality - DNS WATCH is for you. It does not require registration and provides additional protection. Nobody can tell you which websites you shouldn't visit. With DNS WATCH services, you no longer need to rely on your ISP when searching the Internet. You can rest assured that no DNS queries are being censored. The service does not register Internet requests, you always remain an anonymous user. There is only one drawback - low speed.

DNS WATCH service page providing DNS services

Norton Connect Safe

Norton ConnectSafe protects your computer from harmful and unwanted Internet resources. Does not require installation of additional hardware and software. It is enough to enter the IP addresses of the DNS service. It is free for non-commercial use.

Video: Protecting Incoming Internet Traffic, Configuring Norton ConnectSafe

Helps secure web browsing:

1. As a product of the Internet security software company Norton, it will provide a reliable barrier against malicious, fraudulent sites.
2. Blocks sites with sexually explicit material.
3. Allows you to restrict children from viewing sites with questionable content.

The service is not a complete replacement for the antivirus program installed on the user's computer. Norton ConnectSafe is your first layer of protection.

Level 3 DNS

The service ranks third in popularity. In addition to DNS services, it offers a large number of other products. Constantly develops new services to help businesses. Leading DNS service provider with flexible and reliable server network responds quickly to customer needs. Uses a combination of public and private connectivity over fiber or cloud. They combine with Layer 3 security solutions to include the required applications, services, and DNS features. Level 3 DNS allows you to create the ideal hybrid Layer 3 networking environment.

Description of the capabilities of the Level 3 DNS service

It is necessary to take into account the fact that the service registers all requests coming from your computer.

Comodo Secure DNS

Comodo Secure DNS is a domain name resolution service that handles DNS queries through its network of redundant DNS servers. It will provide a much more reliable connection than your ISP's servers. If you choose to use Comodo Secure DNS, your PC's network settings will be changed so that all applications that access the Internet will use Comodo Secure DNS servers.

Description of the features provided to Comodo Secure DNS users

Comodo Secure DNS gives you a safer, smarter and faster internet. He uses:

• reliable server infrastructure;
• highly structured DNS and Comodo man pages;
• domain name filtering functions;
• Secure DNS refers to the list of blocked sites for dangerous sites.

Most additional features are available for a fee.

Open NIC DNS

Non-commercial project, does not charge for access to DNS services. Fully run by volunteers, and free for users. No government can stop you from visiting your favorite sites. By starting to use the OpenNIC DNS servers provided by volunteers, you can be sure that your connection will not be censored. The service has a huge network infrastructure, you can connect to the server closest to you. You just need to select it from the list.

Description of the purpose and policy of the Open NIC DNS service

DNS setup

Having familiarized yourself with the capabilities of the services that provide their servers, choose the most suitable one, in your opinion. Use the table with IP addresses to configure alternative DNS.

Table: IP addresses of alternative DNS servers

Having chosen the appropriate service, you can start changing the DNS settings:

1. Move the mouse cursor over the "Network" icon and left-click.

   The "Network" icon indicates the presence of an Internet connection

2. In the "Current Connections" tab that appears, select "Network and Sharing Center" and click the left mouse button.

   Left-click on the "Network and Sharing Center"

3. In the new window, select "Local Area Connection".

   On the "View basic information about the network status" tab, left-click the "Local Area Connection" item

4. A new tab will appear, click "Properties".

   On the tab that appears, click "Properties"

5. Select "Internet Protocol Version 4 (TCP / IP 4)", click the "Properties" button again.

   Select "Internet Protocol Version 4 (TCP / IP 4)" and click "Properties"

6. In a new tab in the item "Use the following DNS server addresses" fill in: "Preferred DNS server" and "Alternative DNS server".

   Fill in the items "Preferred DNS server" and "Alternative DNS server", click "OK"

7. Check "Confirm parameters on exit".
8. Press the "OK" button, restart the computer.

Common DNS Errors and How to Fix Them

There are several common DNS errors that users encounter from time to time:

1. The DNS server is not responding, the DNS address of the server cannot be found.
2. Windows is unable to communicate with a device or resource.
3. There is no access to the DNS server.

If an error occurs, first of all, you need to check if the Internet cable has fallen out of the computer. If everything is ok, try connecting it directly, bypassing the router. If everything works without a router, try restarting it. There are many varieties of these devices, but in general terms, the settings for all are almost the same. We will consider how to do this using the example of one of the models of the well-known TP-Link brand:

1. Enter 192.168.0.1 into the address bar of your browser and click search.

   Enter the IP address of the router into the address bar of the browser

2. In the window that appears, enter your username and password (by default "admin", if the password has been changed, you must remember it).

   Enter your username and password correctly

3. Click the "Login" button.
4. In the appeared control panel of the router, select the "System Tools" item.

   In the menu that opens, select "System Tools"

5. The next window will open, in it click the "Restart" item.

   In the "System Tools" section, click "Restart"

6. In the next tab, the message "Press this button to reboot the device" will appear, press the button, confirm the reboot, wait.

After rebooting the router, the error should be gone. Elementary device failures occur quite often, do not rush to panic, any problem can be solved on your own.

Quite often, various DNS errors are caused by problems with your ISP's servers. If you have already taken the steps listed above, but the error message has not disappeared - call your provider, perhaps the reason lies in the incorrect operation of its DNS server.

If the provider's equipment is working, the router is working properly, the network is available, and the browser continues to display an error, the following actions will help:

• ask your friends and download the KVRT antivirus utility to removable media, scan your computer, remove malicious codes;
• set the DNS address as described in the previous part of the article;
• update the network card drivers.

How to determine the IP address of a site by its domain name

Sometimes there are situations in which it is necessary to find out the IP-address of the site. This is not difficult. The easiest way is to install browser add-ons. Take the Mozilla Firefox browser as an example.

Your procedure:

1. Go to the browser settings, select the "add-ons" item.

   In the add-ons installation window, click the Add to Firefox button

A globe-shaped icon will appear in the search column at the top of the browser. To determine the IP address of the desired site, just open its page. Move the mouse cursor over the icon and press the left button.

You will find out the IP address of the site by clicking on the IP finder icon

Another way to set the site url is to use Windows tools:

Both methods are quite simple to perform, but in the second option, be careful - do not rush, enter the command and resource names correctly.

The comfort and convenience of using the Internet largely depends on you. With a minimum of effort, you will get rid of many problems and get the opportunity to reach a new, higher level of network surfing. It is very easy to get away from the shortcomings that are common among the DNS servers of our providers. Switch to alternative DNCs.

When talking about securing your internet connection or accessing blocked content in your geographic area, you've probably heard of DNS. Although all providers supply their own DNS server by default, you can use an alternative one. DNS service is used to determine the IP addresses of sites by their domain. Everything is very simple - in fact, there are no letter addresses like a website on the Internet, all communications and messages between computers are carried out by an IP address. To determine it by domain name, DNS servers are used, which store a huge table of correspondence between domain names and IP addresses.

There are several advantages to using an alternate DNS server:

• The closer you are to the DNS server, the faster the name resolution will be.
• If the provider's DNS is not very reliable, an alternative DNS will improve stability.
• You will get rid of restrictions on access to content based on geographic location.

If you are interested in these reasons, or at least one of them, it's time to set up a DNS server on your system. In this article, we will talk about how to set up a DNS server in Linux, how to find out how fast it is, and also take a look at the best DNS servers. You can choose the best one depending on your needs.

Since our site is still about Linux, let's look at how to configure Linux DNS servers. DNS server settings in any Linux distribution are located in the /etc/resolv.conf file. The DNS server address is specified in the following format:

nameserver 192.168.137.1

Here 192.168.137.1 is the address of the DNS server. But the setting in this file will only work until a reboot, since this file is regenerated on every system boot.

If you are using NetworkManager, you can configure the DNS server there in the connection properties. Open the network connection settings, click in the context menu ANDchange for the required connection, then on the IPv4 tab specify the required DNS server:

Now the settings are saved even after a reboot.

You can test the speed of the DNS server using the utility nsloockup... For instance:

time nslookup www.google.com 208.67.222.222

Server: 208.67.222.222
Address: 208.67.222.222 # 53
Non-authoritative answer:
Name: www.google.com
Address: 173.194.113.209
Name: www.google.com
Address: 173.194.113.212
Name: www.google.com
Address: 173.194.113.210
Name: www.google.com
Address: 173.194.113.211
Name: www.google.com
Address: 173.194.113.208
real 0m0.073s
user 0m0.012s
sys 0m0.004s

The first parameter is the address of the site that we will measure, the second is the address of the DNS server. Team time measures execution time nslookup in milliseconds. Now let's go directly to the list of "good DNS servers".

Best DNS Servers

1. Google Public DNS

The first DNS server on our list is the one from Google - Google Public DNS. It has been in operation since December 2009 and its goal is to make the user experience on the Internet faster, safer and more convenient. It is currently the largest government DNS structure in the world. To use Google Public DNS, it is sufficient to use the DNS server IP address 8.8.8.8 or 8.8.4.4.

Switching to Google Public DNS increases security and optimizes performance because Google actually uses Anycast routing to find the nearest server. In addition, it is resistant to DNS Cache attacks as well as DoS.

2. OpenDNS

If you're looking for more than just a replacement for regular DNS, but an advanced version that gives you more control, try OpenDNS. As the post from this company says, you will take another step towards security by implementing this service. There are two options for OpenDNS - home and corporate. The home version comes with parental controls, phishing protection, and improved speed. The enterprise version of OpenDNS has full functionality for securing an enterprise network. For home use, you can get OpenDNS for free. To configure Linux DNS servers, simply set the following DNS addresses: 208.67.222.222 and 208.67.220.220. OpenDNS also supports Anycast.

3. DNS.WATCH

DNS.WATCH is a minimalistic DNS service that allows you to have fast, uncensored internet access. Since this service is built on the principles of freedom, you can be sure that your request will succeed and no redirects will be used. The server is fast and stable. If you live in a censored country, this would be a great solution. DNS service servers: 82.200.69.80 and 84.200.70.40.

4. Norton ConnectSafe

Norton ConnectSafe is another DNS service designed to harden your internet. It should be noted that Norton has been dealing with the security aspects of many devices for a long time. Therefore, you can be confident in the quality of Norton ConnectSafe. The service offers three different protection options: protection against malware, phishing and scams, protection against pornography and other threats. Different IP addresses are used for each species. To protect your entire home network, you just need to set up your router.

5. Level3 DNS

Level3 DNS is a great DNS service if you are looking for a reliable DNS server with excellent performance. While Level3 isn't as big as Google, it has an impressive infrastructure. You can be sure that the speed will be top notch. DNS server IP addresses: 209.244.0.3, 209.244.0.4, 4.2.2.1, 4.2.2.2, 4.2.2.3 and 4.2.2.4.

6. Comodo Secure DNS

Comodo Secure DNS is another service that combines speed, reliability and security. Comodo uses a huge network that includes a large number of DNS servers. The speed will be optimized by choosing a server based on your location. In addition, Comodo takes care of security by supplying a list of dangerous sites, and the DNS service will make sure that you do not visit any of them. Comodo Secure DNS IP addresses are 8.26.56.26 and 8.20.247.20.

7. OpenNIC DNS

Although OpenNIC DNS is last on the list, it is a great solution if you want free internet access without government censorship. OpenNIC DNS has a very large network infrastructure, and therefore, it will most likely find a DNS server close to your physical location. Just select the server you want from the list.

conclusions

As you can see, some of these servers provide regular DNS bypassing the provider's bans, while others have additional features - protection against attacks, phishing and dangerous programs. They are all the best DNS servers and you can choose one of them depending on your needs.

DNS is a service that provides exchange between different network segments. Its use can significantly reduce the time spent searching for information. In this article, you will learn about the basic principles of the service, as well as the methods and forms of data transmission on the Internet.

How does it work

At the dawn of the Internet, there was a "flat" naming system: each user had a separate file that contained lists of contacts he needed. When he connected to the World Wide Web, his data was sent to other devices.

However, due to the rapid development of the Internet, it was necessary to simplify the exchange of data as much as possible. Therefore, it was divided into smaller segments-domains. In turn, they are divided into subdomains. At the top of the address submitted in the nominal form is the root - the main domain.

Since the Internet is an American development, there are two types of primary domains:

• generic domains that belong to US institutions:

1. com - business organizations;
2. gov - government offices;
3. edu - educational institutions;
4. mil - military missions;
5. org - private organizations;
6. net - internet service provider.

• other country's indigenous domains are two-letter.

The second level consists of abbreviations for cities or regions, and the third-order domains denote various organizations and businesses.

The dot acts as a separator between domains of different order. There is no full stop at the end of the name. Each individual dotted domain is called a label.

Its length must not exceed 63 characters, and the total length of the address is 255 characters. Basically, Latin, numbers and the hyphen sign are used, but several years ago they began to use prefixes based on other writing systems. The letter case does not matter.

Servers are computers that contain a list of other objects within one level of the network, which makes it possible to speed up the exchange between users. They became the basis of the new system.

Each layer of the network must have its own server, which contains information about the addresses of users of its segment.

The search for the required data is as follows:

DNS basics

A multi-domain host is called a zone... Its file contains the main parameters of its segment. This includes FQDN or Fully Qualified Domain Name (FQDN) information. If such an entry ends with a period, it means that the name of the object is specified correctly.

There are several types of computers that serve DNS:

• master- the main agent of the network. He can change its configuration;
• slave- devices of the second order. They serve clients on a par with master and can replace it in case of failure. This relieves the load on the network;
• caching. Contains in its information about domains of extraneous zones;
• invisible. Not in the description of the zone. Most often, this status is assigned to users with the master status in order to protect them from attack.

The user can send one of two types of requests to them.

The browser sends it through the resolver program:

• recursive. If the server does not contain the necessary information, in this case it learns the necessary data from higher-level computers and sends a response to the client. This allows you to reduce the number of requests and saves time and your traffic;
• iterative. The server sends a ready answer, selecting information only from its own cache (memory). If he does not have suitable data, then he provides a link to other computers. The browser then navigates to that address.

There are two types of responses:

1. authoritative- if data is sent from devices that serve the network;
2. non-authoritative. It is sent by an outside computer that receives the necessary data from its own cache or after an iterative request.

Video: DNS Service

Names and IP addresses

DNS provides translation of site names into IP addresses. On the Internet, every device can be tracked by 2 main parameters - domain name and IP address. They can be assigned to a user's computer, network printer, or router.

However, this is rather arbitrary, since a computer may not have a domain name, but use several addresses. In addition, each IP address must match all domain names. However, a domain can only contain information about one IP address.

Working hours

Servers can operate in the following modes:

1. maintenance of your own zone. Data exchange takes place between master and slave computers. In this case, requests from non-authoritative users are not accepted;
2. executing a recursive question;
3. forwarding- the server sends a request to another zone.

Changing DNS parameters

Typically, these parameters are set automatically by the network. In order to reset the data, you need to go to the "Network Connections" section.

Photo: changing DNS server parameters

After that, you need to go into the protocol used to maintain the network.

In the "Properties" section, you can set the required parameters. Usually, the main IP address of the server and the alternate one are indicated.

Message format

The messages that are used to exchange information by the service begin with a 12-byte header. This is followed by an identification field that allows you to determine which request the response came to.

The flags field (next 16 bits) includes information:

1. message type;
2. operation code;
3. identification of authority (i.e. shows whether the serving computer belongs to the network);
4. TC flag. Displays whether the message arrived truncated or complete.
5. recursion flag, i.e. requests the server to send requests to higher-order computers;
6. recursion capability flag. Indicates the server's ability to forward messages;
7. return code. Displays whether a response was sent with errors or not.

The last 16-bit field shows the total number of parameters taken into account.

DNS query questions

Part of a resource record in a response

Any response contains information about the party that sent the message. It contains the following data: response, server credentials and additional information about it.

In addition to them, the message contains:

• domain name;
• type of request;
• the expiration date of the cached version;
• resource record length - an estimate of the amount of information.

Pointer Requests

Pointer queries are directed to find the page in inverse mode, i.e. search for a resource name by IP address, given as a dot-delimited text string.

To send it, the host address is written in the opposite order with the addition of a specific suffix (most often in the form in-addr.arpa).

The operation can be performed if the resource contains a PTR record. This allows you to transfer control of the zone to the owner of the IP addresses.

Resource records

This is a list of the main programs used by the service. These records are unique within the same domain. Duplicates of these records may exist at different levels of the network.

This data includes the following types of records:

1. SOA–Start of powers. It allows you to match the domain and the computers serving it. They also contain information about the expiration date of the cached version, and the contact person who serves the server of a certain level;
2. And contain a list of IP addresses and their corresponding hosts. They allow you to identify the address of domain resources;
3. NS (Name Server) include a list of computers that serve the domain;
4. SRV (Service) displays all the resources that perform the most important functions of the service;
5. MX (Mail Exchanger) allow you to automatically configure the distribution of data to serving computers within the same domain;
6. PTR (Pointer) are used to find the name of a resource if the user knows its IP address;
7. CNAME (Canonical Name) allow a server to be referred to by multiple aliases in a service.

Caching

To find the information you need, the browser can search for information in three segments. First, the required data is searched using a DNS service, i.e. at the local level. They can be found if the computer contains a Hosts file.

However, if the operation fails, then the client issues a request. To speed up the search for information, cached servers are used. If it does not find the data it needs, then it executes a recursive query. When filing, it copies data from other networks.

Photo: setting up a caching DNS server

This allows you to save traffic by not subsequently turning to authoritative users. But an open record remains valid for a limited time. Its expiration date is set in the zone file. By default, the minimum is 1 hour.

UDP or TCP

The service supports both UDP and TCP.

UDP is used to send messages over wide area networks. The size of messages sent via this protocol is limited. Incomplete responses contain the TS tag. This means that the response size exceeded 512 bytes, so the rest did not reach the computer.

It is less reliable because it does not have a specific request response timeout. However, such a system is suitable for transmitting a huge amount of information.

TCP is used to transmit such data because it allows any amount of data to be received, divided into segments of a certain size.

It is also used by secondary servers when they request data from the host computers every three hours to find out if the network configuration file has been updated.

DNS has a complex hierarchical structure. However, the server system provides flexible and fast interaction between all users and devices of the Network.

To find out the necessary information, the client sends a request. The response contains basic information about the object of interest and the computer serving the zone. To carry out this exchange, the UDP and TCP protocols are used.

The Internet is a network in which each personal computer is associated with a certain personal number, which is called an IP address. Digital addressing was not the most convenient at the dawn of the development and formation of the Internet, so it was decided to use letters to write addresses. That is why, when a person decides to go to any site, he enters letters, not numbers. The problem is that a computer can only perceive information in digital form - a sequence of zeroes and ones. He is a priori unable to understand information in the form of letters. Therefore, a service was created, whose main task was to translate the alphabetic spelling of addresses into the form of numbers. And this service was named DNS (in decryption it means Domain Name System). But how does it work? What is DNS?

What is this service?

So what is DNS? It is a huge database of information about whether a domain name matches an IP address or not. DNS is the so-called protocol, which is a computer, clearly distributed system aimed at obtaining information about the various states of a particular domain. Translated from English, Domain Name System means "domain name system". All this information is stored by the so-called DNS server. This protocol is often used to obtain an IP address based on the name of a particular host (the host can be a computer or other device with Internet access). What is DNS besides this? Also, this service is necessary to obtain information on demand about the route that the mail has passed, served by nodes under the protocols in the domain.

Hierarchical structure

What is DNS? It is a domain name system, which is a distributed database. It is supported because there is a clear and harmonious hierarchy of servers interacting with each other according to their internal protocols. Each DNS server is based on a system “view” of the hierarchy of domain addresses in different zones. Each server that is responsible for a particular name can delegate responsibility for possible new parts of the domain to some other servers. This helps shift responsibility for popular content to servers across businesses, individuals, and organizations that will only be responsible for their own portion of the common domain name.

Protection

Several years ago, tools began to appear in domain name systems for verifying the integrity of transmitted data. These tools became known as Security Extensions. The information that is transmitted is not encrypted, but the reliability of the data is checked using cryptographic methods. An implemented standard called DANE transmits reliable cryptographic data. They are then used to establish secure and secure transport and application layer connections. Domain and server owners should periodically update their DNS firmware to ensure reliable verification and a decent level of protection for transmitted information. Otherwise, the safety and reliability of the data may not be guaranteed.

What functions does CSN perform?

What is DNS and what are the functions of this protocol?

1. Distribution of administration. This means that different organizations and people are responsible for their parts of the structure.

2. Distribution of information that is stored. Each network node must separately store not only the information that is in its area of ​​responsibility, but also other addresses from the so-called "root" servers.

3. Data caching. Certain nodes are able to store a certain amount of data from non-proprietary areas of responsibility to reduce network loads.

4. Creation and maintenance of a hierarchy structure, where all nodes are connected into a single tree, in which each node is able to determine the work of the underlying nodes, delegate authority to other adjacent nodes.

5. Redundancy - storage and maintenance of own zones, for which several DNS servers are responsible. They are divided into logical and physical, which guarantees the absolute safety of information and the ability to continue working in the event of a failure of one node.

DNS system operation

What is DNS and how does it work? This mechanism is adopted because the domain name has different addresses. Every server on the Internet has an IP, which is a set of numbers. Each time, changing the provider, the user changes the hosting and with it the server, as well as the IP address. Sometimes, for normal operation on the Internet, it is necessary to update the driver on the computer. DNS (Domain Name Server) stores a record of the user's domain name and IP to which queries are to be sent. When a user fills out a DNS record in his domain, he provides information about the location of his site. And when for the first time there is a hosting opening or domain name registration, information about the resulting record is sent to all other servers. Maybe the site will work right away, but on average, information is distributed within two or three days. This delay occurs because many domain name servers are configured to update data over a period of time.

What is a DNS server, how does a DNS server work?

What is a DNS server

A DNS server is a server that translates symbolic domain names into IP addresses and vice versa.

A domain is a specific zone in the domain name space, which must be assigned at least one IP address.

How DNS works

DNS service is used to map a domain name to an IP address. The DNS system consists of many servers of different levels, each network must have its own DNS server, which contains a local database of DNS records.

How it works:

• The client makes a request to the local DNS server, for example, in the address bar of the browser you typed the site address;
• If the local DNS contains this record, then it gives the answer. In our example, the browser will receive the IP address of the site and access it.
• If there is no required record in the local DNS, then it turns to the next DNS server, and so on, until the record is found.

Many domain names can be associated with one IP address - this is called virtual hosting. But one domain name can be assigned multiple IP addresses, usually for load balancing.

DNS server records

The DNS server has several types of records, consider them:

SOA record creates a zone for a domain, for example, we need to add the domain exempl.com, then we first need to create an SOA record that will indicate on which server information about this domain is stored. The SOA record has several parameters:

1. Serial - serial number of the zone. It increases every time you make changes in this domain, this is necessary to determine the changes from the secondary DNS server and determine the need to update your cache.
2. Refresh - update period. The period, in seconds, after which the secondary DNS server should check the serial number of the primary server for changes, and update the data if required.
3. Retry - retry update. Sets the frequency of attempts to update the secondary DNS when there is an error connecting to the primary. Set in seconds.
4. Expire - the period of storage of primary DNS data on the secondary, in case of unsuccessful attempts to connect and update data.
5. TTL is the lifetime of records for this zone in the cache of secondary DNS servers. For example, the lifetime A of a record for a given zone on secondary servers. If the data changes frequently, it is recommended to set a small value.

NS record(name server) - points to the DNS server for this domain, that is, to the server where A records are stored.

example.com IN NS ns1.ukraine.com.ua

Record A(address record) - this record indicates the IP address of the domain.

example.com IN A 91.206.200.221

CNAME record(canonical name record) indicates a synonym for this domain, that is, this domain will be assigned the IP address of the domain to which this record refers.

example.com IN CNAME xdroid.org.ua

MX record(mail exchange) points to the mail server for this domain.

example.com IN MX 10 mail.example.com

The extra digit before mail.example.com indicates the value of the priority - the lower the digit, the higher the priority.

PTR record(Pointer) - is the reverse of the A record. The IP address by domain is searched for by the A record, and the domain by the IP address by the PTR records. It makes sense to put PTR records only on physical hosting, since all names have the same IP on shared hosting.

This is not a complete list of DNS server records, but we have covered the main records.

Complete list of DNS records:

1. SOA (start of authority record)
2. NS (name server)
3. MX (mail exchange)
4. A (address record)
5. CNAME (canonical name record)
6. TXT (Text)
7. PTR (Pointer)
8. SRV (Server selection)
9. AAAA (IPv6 address record)
10. AFSDB (AFS data base location)
11. ATMA (ATM address)
12. DNAME (Name redirection)
13. HINFO (Host information)
14. ISDN (ISDN address)
15. LOC (Location information)
16. MB (Mailbox)
17. MG (Mail Group Member)
18. MINFO (Mailbox or Mail list info)
19. MR (Mail rename)
20. NAPTR (Naming Authority Pointer)
21. NSAP (NSAP address)
22. RP (Responsible Person)
23. RT (Route through)
24. SPF (Sender Policy Framework)
25. SRV (Server Selection)
26. X25 (X.25 PSDN address)