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

Good day, dear subscribers and guests of the blog. You've probably heard the acronym DNS and probably understand the basics. However, for many it is a confusing term. Therefore, today I will try to explain as clearly as possible what a DNS server is and how to configure it, I will tell you the principles of its operation and why it is needed. Let's get started!

Meet us! DNS

So DNS stands for "Domain Name System". If you know English, then you already understand what will be discussed. The term translates as "Domain Name System". This is a kind of distributed storage, a database in which keys and values ​​are stored, or rather IP addresses and their corresponding domain names. To understand why this is needed, let’s take a moment to dive into history.

We use all this every day. Thanks to this technology, we easily navigate through services and quickly find the information we need without hesitation. And all because every resource on the Internet has its own IP address, which looks, for example, like this: 87.245.200.148, and the corresponding .

In this case it is www.google.com.ua. This system appeared because it is not convenient for network users to remember the numeric addresses of sites. Thus, when a user enters a specific website name in the DNS system, a complex process of searching for its IP occurs and vice versa. By the way, one IP address can be assigned several domain names, and vice versa, one domain name can be assigned many IP addresses.

Previously, such information was recorded in one single file and stored by users on local computers. However, the World Wide Web grew and this method quickly became irrelevant. It was replaced by a domain name system developed in the second half of the 20th century by Paul Mockapetris.

Domain Name System consists of many levels, each of which has its own domain records. It is interesting that the higher the domain hierarchy, the further to the right it is located when writing the site address.

The root of such a hierarchical tree is the dot – “.”. It is followed by first-level domains. These include the following names: org, com, net, int, edu, gov, info, pl and others. This also includes the indication of the country. For example, ru, ua, etc. Next come the next levels.

Due to the huge number of domains, they were all divided into zones - a certain part of the names that is stored as a whole on one or more DNS servers.

When performing some kind of request on the Internet, a very interesting and complex thing happens. When a user sends a request, it is sent to the server. The server, in turn, checks whether it can produce the result.

If it cannot determine the answer, it forwards the request further to the root or higher-level DNS server. This upward movement is called “Ascending Hierarchy.” After obtaining the required result, the movement changes its direction and reverse order transmits information.

By the way, depending on the method of issuing a response, DNS servers are divided into two types: recursive and non-recursive (iterative). In short, the first type of request performs a full search of all references to various servers and independently queries them, and then caches all received records. In the second case, the referrals are returned to the user and he must check them himself.

I only told you general principles functioning of DNS, which provide insight into what is happening in . However, this is not all.

Why set up a DNS server for your website?

As I already said, each site has its own IP address and domain name. Depending on how often you move to a new hosting, the server also changes. This means that the IP also changes. Therefore, the key-value relationship is not constant.

And if you do not configure all of the listed indicators, then your resource will become unavailable for search, since it will not respond when called to the old address. In another case, if the DNS records about your resource are deleted from the old one, then the domain name will send network users into the void and then the last error will be displayed.

Therefore, when changing providers, be sure to update information about the location of your site: check the domain, IP value and all other parameters.

If you have done everything as written above, but no changes have occurred, do not be alarmed. New instructions for connecting to the site take quite a long time to take effect. This may take from 24 to 72 hours. Although some people are very lucky and registration takes about 5 hours. Why is this so?

It all depends on which DNS servers and at what time the information will be updated. When new parameters are entered, these records are transferred to other domain name servers and the old data is overwritten there. However, many DNS are configured to periodically update information, which results in a delay in updating data.

Of course, other problems happen when you change the address of a web resource and you don’t always know for sure how to correct the situation. To do this, they provide their customers with technical support. And advanced resource owners can find a solution themselves over time.

On this note, I bid you farewell. Subscribe to my blog updates. Thank you in advance for the reposts. Bye bye!

Best regards, Roman Chueshov

What is DNS?

DNS stands forDomain Name System or Domain Name Service. You specified a name, and DNS substitutes the IP address of the resource on which the site is hosted. The name in this case is the host name or IP address. Without DNS, you would have to remember the IP address of every website you want to visit. Today there are more than 300 million websites on the Internet, it is absolutely impossible to remember the IP address of the required site.

What is dynamic IP?

How to make a static IP address from a dynamic one?

There is no need to buy a static IP. Use our free Dynamic DNS to map a dynamic address or long URL to your resource so you can easily remember the hostname. Remote monitoring of your home via a webcam on any port or running your own server at your home with a dynamic IP address - all this is available with the serviceDnsIP . If a provider allocates a dynamic IP, a service such as Dynamic DNS becomes necessary.

When you register on our service, you receive a domain name. A special client that needs to be downloaded is installed on the user's computer. This client periodically sends information to the DNS server, reporting its IP address. The DynDNS service server stores the user's last IP and, when accessing the user domain name received during registration, redirects the request to this IP.

Private network.

Regular services offer only third-level domain names. This may be inconvenient. If you have an external dynamic IP address, our innovative project allows you to get a domain name not only of the third, but also of the first level. By installing a special application on your computers, you will have access to a private network in which you will be able to access services or programs using any protocol or port. In this case, no traffic will pass through our server. All information will be transferred between computers directly.

Remote computer and remote desktop.

By using DynDNS Secure service DnsIP allows you to organize a connection to a remote computer through any program remote access using any port. In this case, you directly communicate with the remote computer, and our service only tells your programs the required IP address.

Network monitoring.

Using our service, you will have access to network monitoring. All connected users (their computer names) will be tracked only by you. You will be informed which computer is online and which has gone offline.

If any application is on remote computer is not responding and there is a need to safely reboot the remote machine, you can do this by pressing a button without using command line and special firewall settings and even if the remote network does not have an external IP address. All you need is an Internet connection.

Automatic click on the free access button when using Yota.

If you use free Internet access from the Yota provider, once a day the connection is blocked and a window appears in the browser asking you to continue at a slow speed. This is extremely inconvenient when using remote access to this computer. In this case, it is enough to install ourfree program, and it will restore Internet access within a few minutes. This option is available without user registration on our website. In this case, the program only needs to be installed, no settings need to be made.

At any time you can find out the IP address of your resource.

At your service is the page http://dns-free.com/dns2ip.php?dns=xxxxxxx, where xxxxxxx is the domain name in the DnsIP system. Use it to organize links to your resource using a dynamic dns system. Or add to favorites, and with one click find out the current ip of your resource. Or enter manually in the form on the same

DNS is a service that facilitates communication 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 operation of the service, as well as methods and forms of data transmission on the Internet.

How does it work

At the dawn of the development 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 data exchange 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, there is a 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 agencies;
  3. edu – educational institutions;
  4. mil – military missions;
  5. org – private organizations;
  6. net – Internet provider.
  • The indigenous domains of other countries consist of two letters.

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

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

Its length should not exceed 63 characters, and the total length of the address should be 255 characters. Basically, the Latin alphabet, numbers and hyphens are used, but several years ago they began to use prefixes based on other writing systems. Letter case does not matter.

Servers are computers that contain a list of other objects within one network level, which allows for faster exchange between users. They became the basis of the new system.

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

Searching for the necessary data goes like this:


DNS Basics

A node consisting of several domains is called a zone. Its file contains the main parameters of its segment. This includes information about the FQDN or fully qualified domain name. If such an entry ends with a dot, this means that the object name is specified correctly.

There are several types of computers that serve DNS:

  • master– main agent of the network. He can change its configuration;
  • slave– second order devices. They serve clients equally with the master and can replace him in case of problems. This allows you to relieve the network;
  • caching. Contains information about domains of foreign zones;
  • invisible. Missing from the zone description. Most often, this status is assigned to users with 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 obtains 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 response, selecting information only from its own cache (memory). If it does not have suitable data, it provides a link to other computers. The browser then goes to this address.

    There are two types of responses:

  1. authoritative– if the data is sent from a device that serves the network;
  2. non-authoritative. Sent by a third-party computer that obtains the necessary data from its own cache or after an iterative request.

Video: DNS Service

Names and IP addresses

The DNS service provides translation of website names into IP addresses. On the Internet, each device can be tracked using 2 main parameters – domain name and IP address. They can be assigned to the user's computer, network printer, or router.

However, this is very conditional, 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.

Operating mode

  1. Servers can operate in the following modes: maintenance of your own zone.
  2. Data exchange takes place between the master and slave computers. However, requests from unauthorized users are not accepted;
  3. performing a recursive question; forwarding

– the server sends a request to another zone.

Changing DNS settings Typically these parameters are set by the network in automatic mode

. In order to reset the data, you need to go to the “Network Connections” section.

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

In the “Properties” section you can set the necessary parameters. Usually the main IP address of the server and an alternative one are indicated.

The message that is used to exchange information between the service begins with a 12-byte header. This is followed by an identification field that allows you to determine which request was answered.

The flags field (the next 16 bits) includes the information:

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

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

Questions in DNS request

Part of the resource record in the response

Any response contains information about the party that sent the message. It contains the following data: response, server credentials and Additional Information about him.

In addition to them, the message contains:

  • domain name;
  • request type;
  • validity period of the cached version;
  • resource record length – an estimate of the amount of information.

Index queries

Pointer queries are aimed at searching for a page in inverse mode, i.e. searching for a resource name by IP address, given as a text string separated by dots.

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

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

Resource records

This is a list of the main programs used by the service. Within one domain, these records are unique. 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 compare a domain and the computers serving it. They also contain information about the validity period of the cached version, and the contact person who services the server of a certain level;
  2. A 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) display all resources that perform essential functions services;
  5. MX (Mail Exchanger) allow you to automatically configure the distribution of data to serving computers within the boundaries of one domain;
  6. PTR (Pointer) used to search for a resource name if the user knows its IP address;
  7. CNAME (Canonical Name) allow the server to be referred to under multiple aliases within the service.

Caching

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

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

This allows you to save traffic without subsequently contacting authoritative users. But an open entry remains valid for a limited period. Its validity period is set in the zone file. The default minimum is 1 hour.

UDP or TCP

The service supports both UDP and TCP protocols.

UDP is used to send messages over global networks. The size of messages sent via this protocol is limited. Incomplete answers contain the TS label. 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 timeout for request response. However, such a system is suitable for transmitting huge amounts of information.

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

This protocol is also used by secondary servers when they request data from host computers every three hours to learn about updates to the network configuration file.

The DNS service 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 data about the object of interest and the computer serving the zone. To carry out this exchange, the UDP and TCP protocols are used.

Before you find out why the DNS server is not responding or unavailable, as well as solving other problems with it, it is important to get information about the server itself or refresh your memory if you have dealt with this before. The DNS server is designed to provide information, communication between computers on the network and other similar operations. The abbreviation DNS itself stands for Domain Name System, which means their totality. For clarity, let's look at a small example.

Sometimes there may be problems with the DNS server, but they can be solved if you follow all the instructions

Let's imagine that all computers on the network are people who are assigned a number at birth (for a PC on the network this is an IP address). For even greater understanding, we will assume that the address in question belongs to some site. So, so that people don’t get confused with numbers, they give each other names. In our case, this will be the name of the site, that is, what you type in address bar browser. But people understand names, but machines need numbers, which is why IP addresses exist. Thus, to ensure this exchange between alphabetic and digital data, a domain name system was invented, which stores in its memory the correspondence of IP addresses and site names. If you access www.google.ru, for example, and the DNS server at your Internet provider has fallen, then you will not go to the site, but will see an error warning. Now, if we understand a little about the essence of this service, we can move on to solving the problem.

Can't find address

What to do if you can’t find the DNS server address? This problem is also very common, but there can be many reasons for its occurrence. Therefore, we will consider the most popular:

  1. First, be sure to check the operation of your router (that is, there may be a problem with the connection you are using). You can reboot your Wi-Fi router or wired modem, then try logging into the site again.
  2. Secondly, you may experience a failure on the provider side, then you should contact them directly. This will significantly save your time and nerves.
  3. The browser used to access the Internet is also important, which may also be the reason why it is not possible to resolve the DNS server address. Try using a different program or application.
  4. If problems occur only on one of your devices, then you should definitely correct its settings. First, you can try to check whether the client service itself is running. Launch Control Panel on your computer or laptop. Open the “Administration” item, where, in turn, launch “Services”. In the “General” tab, check the following parameters: startup type should be automatic, status “Running”. If it is turned off, then click the “Run” button in the same window.
  5. If you cannot find the server address on only one or two sites, then it is likely that the error lies in the site itself. Then it will be enough to wait some time until the work is restored. It's also worth trying out on multiple devices. If the problem occurs at all, then we turn to the second point above.
  6. If the methods described above do not help, try using the Microsoft FixIt utility, which can be downloaded for free from the official website (http://support.microsoft.com/kb/299357/ru). It can also help if you are unable to resolve the server's DNS address.

DNS server is not responding

So what should you do if your DNS server isn't responding? Now we will solve this unpleasant problem. Please note that this solution is also suitable if the server's DNS address cannot be resolved. We will look at several ways to eliminate this problem, since, unfortunately, there is no single “life preserver”.

Switch to DNS from Google

  1. First, you will need to clarify the question: is the DNS client running on your device (computer or laptop)? To do this, write “Run” in the “Start” search bar and run the found utility. In the field of the window that appears, enter services.msc. Now, in the list of services that appears, find the client we need. If it has an automatic startup option and operating status, then move on to the next point. Otherwise, set these items according to the specified criteria.
  2. Next, you will need to switch to public domain name systems from search giant Google. The only thing you should pay attention to is that when working with some providers, redirection to a page with a notification about the end of funds in your personal account may not work. But if this is not a critical problem for you, and the correct operation of the server is more important to you, then we will describe to you how to do this.
  3. Launch Network and Sharing Center shared access» in the computer control panel. Open the “Change adapter settings” tab, where you need to select the one from which your Internet works. If you have both a wired and wireless connection, then configure both adapters just in case to avoid conflict situations.
  4. Right-click on it and in properties select “Internet Protocol Version 4”, where we will also need properties.
  5. In the "General" tab, enter the following parameters:
  • The preferred DNS server will be 8.8.8.8
  • The alternative will be the following: 8.8.4.4
  1. Click OK and close all settings. Check if the problem is resolved. Usually, in most cases, switching to Google's DNS helps when the DNS server does not respond or the server's DNS address cannot be resolved. Therefore, we hope that everything was resolved successfully for you too.

Solving problems for other reasons

  1. Network problems. You need to check that the server has an active allowed connection: check the client’s hardware settings, as well as their serviceability. Make sure you can communicate with other devices or modems that are on the same network as the DNS server. To do this, you can easily use the ping command.
  2. If the previous solution did not help, then you need to perform an additional check. Using the nslookup command, check the ability of your server to respond to clients themselves if the DNS server does not respond.
  3. It happens that the browser writes that it cannot find the address. It is possible that the IP address you are interested in simply needs to be added to the list of restricted interfaces for the server (addresses allowed for servicing). This solution will help those users who had a setting on the server to limit the IP addresses that need a response.
  4. Be sure to check your computer for viruses or malicious codes using a special anti-virus utility. Very often, computer or network problems arise due to viruses on your PC or laptop. Therefore, do not omit this item under any circumstances and conduct a deep scan and, if necessary, clean up of infected files.

Conclusion

Dear friends, today we learned how to solve several problems, namely, what to do if: the DNS server does not respond or is unavailable, you cannot find the DNS server address or convert the DNS server address. We hope that you were able to resolve this issue and it no longer torments you with its presence. Please note that most methods are suitable in almost all cases, so try using universal solutions first and then specific solutions.

When talking about securing your Internet connection or accessing blocked content in your geographic area, you've probably heard about DNS. Although all providers provide their own default DNS server, you can use an alternative one. The DNS service is used to determine the IP addresses of websites based on their domain. It’s all very simple - in fact, there are no alphabetic addresses like a website on the Internet; all communications and messages between computers are carried out via 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.

Using an alternative DNS server provides several benefits:

  • The closer you are to the DNS server, the faster name resolution will be.
  • If your 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 these reasons, or at least one of them, interest you, 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 its speed, and also 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 set up Linux DNS servers. The 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 DNS server address. But the setting in this file will only work until you reboot, since this file is regenerated every time the system boots.

If you use NetworkManager, you can configure the DNS server there, in the connection properties. Open Settings network connections, click in context menu ANDchange for the desired connection, then on the IPv4 tab specify the desired DNS server:

Now the settings are saved even after a reboot.

You can test the speed of the DNS server using the utility nslookup. For example:

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 DNS server address. Team time measures execution time nslookup in milliseconds. Now let’s move directly to the list of “good DNS servers”.

Best DNS Servers

1. Google Public DNS

The first DNS server on our list is a server from Google - Google Public DNS. It has been operating since December 2009 and its goal is to make users' online experience faster, safer and more convenient. It is currently the largest government DNS entity in the world. To use Google Public DNS, you only need to use the DNS server IP address 8.8.8.8 or 8.8.4.4.

Switching to Google Public DNS improves security and optimizes speed because Google actually uses Anycast routing to find the nearest server. Additionally, it is resistant to DNS Cache attacks as well as DoS.

2.OpenDNS

If you're not just looking for a replacement for regular DNS, but an advanced version that gives you more control, try OpenDNS. According to the company, you will take another step towards security by implementing this service. There are two options for OpenDNS - home and corporate. Home version comes with parental control, phishing protection and improved speed. The enterprise version of OpenDNS has full functionality to protect the enterprise network. For home use, you can get OpenDNS for free. To configure Linux DNS servers simply install 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 access to the Internet without censorship. Because this service is built on freedom principles, you can be sure that your request will reach its target and no redirects will be used. The server is fast and stable. If you live in a censored country, this will 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 enhance your Internet security. It should be noted that Norton has been involved in the security aspects of many devices for a long time. So you can be confident in the quality of Norton ConnectSafe. The service offers three different protection options: protection from malware, phishing and scams, protection against pornography and other threats. For each type we use different IP addresses. To protect all home network It's easy enough to configure the 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 at top level. 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. Speed ​​will be optimized by selecting 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: 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 access to the Internet without government censorship. OpenNIC DNS has a very large network infrastructure and therefore will most likely find a DNS server that is close to your physical location. Just select the desired server from the list.

conclusions

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

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