Enabling and configuring the DNS server. Why do difficulties arise with the DNS server and who does this happen to? Reserved domain names

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 unload 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.

Typically, these parameters are set automatically by the network. 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.

Message Format

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 it.

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 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 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.

Computers on the network (including the Internet) do not have names; data transfer is carried out using IP addresses.

IP address(Internet Protocol Address) - a numeric address on the Internet, looking like 123.123.123.123. IP addresses are difficult for humans to remember, especially when you visit dozens of sites a day with different IP addresses.

Similar to how you save phone numbers, you can keep a contact book or phone directory for IP addresses. The role of a telephone directory on the Internet is performed by DNS(Domain Name System), domain name system. When you enter a domain name in an Internet browser, it is converted via DNS to an IP address, which is used to access the server.

In fact, DNS servers store not only the IP address of the server, but also other data such as DNS resource records “MX”, “TXT”, “A”, “CNAME”, “SOA”.

DNS servers, which store information about thousands or millions of domains, are often hosted on separate, powerful servers. In such cases, the expression “DNS server” can mean the entire software and hardware complex (server and program itself).

Why register DNS servers for a domain?

When you register a new domain name, no DNS server on the Internet knows about it. And until information about your domain appears on the Internet DNS servers, neither the website, nor the mail, nor any other services will work.

In order for DNS servers on the Internet to know about your domain, someone must tell them, and this someone is the DNS server that you register for your domain. It plays the role of a “herald” who always keeps the latest information about your domain. For example, the hosting DNS servers ns1.hosting.site and ns2.hosting.site store information about domains that are connected to the hosting site.

About the differences between DNS servers ns1.hosting..hosting.site And ns1..site and read about which of these pairs is right for you.

DNS servers are registered in pairs, this is done for better fault tolerance: if one DNS server fails, the other will remain working.

Scheme for determining an IP address by domain name

This diagram briefly explains what happens when you want to visit a particular site.

1. 1 Your computer contacts the DNS servers of your Internet service provider ( arrow 1). The provider's DNS servers look for the IP address in their cache (an intermediate buffer with fast access) and, if they find it, they give you this IP and via IP your computer accesses the server on which the site is hosted ( arrow 7).
2. 2 If the “domain-IP address” pair is not in the cache, then the provider’s DNS server makes recursive queries to the root DNS servers ( arrow 2), of which there are only a few around the world. Changes in domain settings on root servers are not updated instantly, but every few hours. For example, changes in the root DNS servers of the RU zone are updated only 4 times a day. Root servers return the addresses of the domain's DNS servers ( arrow 3) on which the DNS zone of the domain is stored.
3. 3 Having received the addresses of DNS servers, the provider makes a request to one of them ( arrow 4), receives the required IP address in response ( arrow 5), stores it in the cache (so that you don’t have to contact the root DNS server every time) and passes it to your browser ( arrow 6).
4. 4 And only now that the browser has the site’s IP address can it contact the hosting server on which the site is located ( arrow 7), and can display it on your computer screen ( arrow 8).

So:

• Information on root servers is updated only a few times a day.
• Internet providers, as a rule, update the DNS server cache no more than once a day (some providers update the cache even less frequently, but usually no more than 72 hours), so if after registering or transferring a domain (changing DNS servers), The site didn't work right away, don't worry - just wait a while.
• To check if DNS has been updated, use .

The above-described structure of DNS operation is greatly simplified; for details, you can refer to the reference literature on the Internet.

DNS stands for Domain Name System, that is, “Domain Name System”. This is a system in which all server domain names are distributed according to a certain hierarchy. Let's figure out what DNS servers are for, how to configure them on Windows 7, what to do if the server does not respond, and how to fix possible errors.

What is DNS and what is it for?

The DNS server stores information about domains. What is it for? The fact is that the computer does not understand our letter designations for network resources. For example, yandex.ru. We call this the site address, but for a computer it is just a set of characters. But the computer perfectly understands IP addresses and how to access them. IP addresses are represented as four numbers of eight characters in the binary number system. For example, 00100010.11110000.00100000.11111110. For convenience, binary IP addresses are written as identical decimal numbers (255.103.0.68).

So, a computer, having an IP address, can immediately access a resource, but remembering four-digit addresses would be difficult. Therefore, special servers were invented that stored a corresponding symbolic designation for each resource IP address. So, when you type a website address into your browser's search bar, the data is sent to the DNS server, which looks for a match to its database.

DNS then sends the required IP address to the computer, and then the browser accesses the network resource directly.

When you configure DNS on your computer, the connection to the network will go through the DNS server, which allows you to protect your computer from viruses, set parental controls, block certain websites, and much more.

How to find out if the DNS server is enabled on your computer

You can find out whether the DNS server is enabled on your computer and its address through the “Control Panel”.

How to install

Video: setting up a DNS server

Why do you need to change the DNS server?

Of course, your provider also has its own DNS server; your connection is defined through this server by default. But standard servers are not always the best choice: they can be very slow or even not work at all. Very often, operator DNS servers cannot cope with the load and crash. Because of this, it is impossible to access the Internet. In addition, standard DNS servers only have the functions of determining IP addresses and converting them to symbolic ones, but they do not have any filtering functions. Third-party DNS servers of large companies (for example, Yandex.DNS) do not have these shortcomings. Their servers are always located in different places, and your connection goes through the nearest one.

Thanks to this, page loading speed increases.

They have a filtering function and implement a parental control function. If you have children, then this is the best option - dubious sites that are not intended for children will become inaccessible to them.

They have a built-in antivirus and a blacklist of sites. So, scam sites and sites containing malware will be blocked and you won't be able to accidentally catch a virus. It sounds a little absurd, because we said that DNS servers are designed to block unwanted resources. But the fact is that Internet providers are forced to deny access to sites banned by Roskomnadzor in their DNS servers. Independent DNS servers Goggle, Yandex and others are not required to do this at all, so various torrent trackers, social networks and other sites will be available for visiting.

How to configure/change DNS

Here you can configure the order in which DNS servers are accessed. Inexperienced users should be explained that there is no one such server that would store all existing Internet addresses. There are too many websites now, so there are many DNS servers. And if the entered address is not found on one DNS server, the computer turns to the next one. So, in Windows you can configure the order in which you access DNS servers.

DNS suffixes can be configured. If you don't know this, then you don't need these settings. DNS suffixes are a very difficult thing to understand and are more important to the providers themselves. In general terms, all URLs are divided into subdomains. For example, server.domain.com. So, com is the first-level domain, domain is the second, server is the third. In theory, domain.com and sever.domain.com are completely different resources, with different IP addresses and different content. However, server.domain.com is still located in the domain.com space, which, in turn, is located inside com. The DNS suffix when accessing the server is domain.com. Even though the IP addresses are different, the server can only be found through domain.com. In Windows, you can configure how suffixes are assigned, which has certain advantages for internal networks. As for the Internet, the creators of DNS servers have already configured everything necessary automatically.

Possible errors and how to fix them

What to do if the server is not responding or is not detected

What should I do if, when I try to access a website, I receive the error “The computer settings are configured correctly, but the device or resource (DNS server) is not responding”? It is possible that the DNS service has been disabled on the computer for some reason. The DNS server you are using may have stopped working.

Doesn't resolve names correctly

If the DNS server does not resolve names or resolves names incorrectly, there are two possible reasons:

1. DNS is not configured correctly. If you definitely have everything configured correctly, then perhaps the error is in the DNS server itself. Change the DNS server, the problem should be solved.
2. Technical problems on the telecom operator’s servers. The solution to the problem is the same: use a different DNS server.

DHCP server: what is it and what are its features

The DHCP server automatically configures network settings. Such servers will help in a home network, so as not to configure each connected computer separately. DHCP independently assigns network parameters to the connected device (including host IP address, gateway IP address and DNS server).

DHCP and DNS are different things. DNS simply processes the request as a symbolic address and transmits the corresponding IP address. DHCP is a much more complex and intelligent system: it organizes devices on the network, independently distributing IP addresses and their order, creating a network ecosystem.

So, we figured out that DNS servers are designed to transmit the IP address of the requested resource. Third-party DNS servers allow you to speed up the Internet (unlike the provider’s standard servers), protect your connection from viruses and scammers, and enable parental controls. Setting up a DNS server is not difficult, and most problems with it can be resolved by switching to a different DNS server.

DNS is a special system for obtaining information about domains (Domain Name System).

Why is DNS needed?

Records (in domain settings) about DNS servers are needed so that any user can find and open your website in their browser.

How does DNS work?

All sites are stored on the servers of hosting providers. Which have hundreds or thousands of servers, and each of them has its own IP address. When a user wants to open a site (for example hostings.info), he enters it in the browser and a request leaves the computer.

First, the request goes to the DNS server, which tells you where you can find out the IP address of the server on which the files of the requested site are stored. The response contains the NS server address (ns1.hoster.com and ns2.hoster.com).

After this, a request is made to the server with IP 218.106.218.10, which processes the user’s request and in response shows the user the site that he wanted to open.

How to use DNS in hosting?

First of all, DNS is used to move a website to a new hosting, or to assign a domain to a specific provider (if the domain is new).

How to configure DNS?

Even if you have little experience, you will soon discover that changing DNS settings is very simple. All you need is to go to the domain control panel (it is located either at the domain registrar or at the hoster [if you registered the domain through it]). And enter the names of the DNS servers there (for example, ns1.hoster.com and ns2.hoster.com), which can be obtained from the hosting provider. But most often they come along with the rest of the settings, in the first letter sent by the hosting provider.

How to find out the current DNS of your or someone else's website?

This can be done using any WHOIS service that we have rated.

Important

The ability to change the DNS settings of your Internet site is important for many users. However, you should be aware that incorrectly entered data into the DNS settings can cause disruption to the site and even its complete inoperability for a long period of time. This is because DNS changes do not take effect immediately. If you entered incorrect data, this will lead to access to the site being blocked not only for its potential visitors, but also for yourself. Once an error has been corrected, it may take up to 72 hours for the adjustments to take effect.

What is a Domain Name Server (DNS)?

The function of a domain name server is that it provides the information necessary for computers to quickly search for the location of sites on the Internet. When a user types an address into a browser, the provider checks the address through a domain name server to know where to send the user's request.

Why is this happening?

This algorithm of actions was adopted due to the fact that a domain name is not always a permanent address. Servers on the Internet have their own IP addresses, which are a specific set of numbers. Every time a site changes hosting provider, this means that it moves to another server, and the new server, accordingly, has its own IP address.

The domain name server stores a record of the site's domain name and the IP address of the server to which requests should be sent.

Why is it necessary to specify the hosting nameserver in the domain record?

A name server is designed to find information about your Internet site. When you register your domain, you automatically tell the Internet the exact location of your site on the Internet. If you do not change the information in your domain record, in other words, leave a mention of the previous hosting provider, then the pointer to the location of your site will point to a server where your site no longer exists. And if your previous provider removed your website's record from their domain name server, then your domain will be redirected to the void.

Why does it take so long for information about hosting changes to take effect?

When a user changes hosting provider or registers a domain name for the first time, the record data is automatically sent to other domain name servers. The site can begin to function 4 hours after registration, but the average time period for disseminating information is from 24 to 72 hours. This situation is due to the fact that, basically, most server names periodically update information. This means that the information stored is not always up to date. Information is updated after a certain period of time, this is due to the fact that information of this level changes extremely rarely.

What to do if the domain links to the previous hosting, although there has been no account there for a long time?

This situation is due to the following possible reasons:

1. Data about the previous DNS is saved in your domain records.

Solution to the problem: you'll need to adjust your domain records so that they point to your current hosting provider's nameserver.

2. your previous hosting provider did not remove records of your domain from its server.

Solution to the problem: you need to ask your old provider to remove the old record for your domain. If your site is already served by a new hosting provider, follow the algorithm of actions indicated in the previous paragraph.

3. Information about the new entry on your website has not yet spread to all nameservers. This situation occurs when you change the nameserver locator entry of your website's domain.

Solution to the problem: wait 24-72 hours, during which time the settings will take effect. However, if the problem persists, contact your new hosting provider.

Why do users see my newly registered website but I still don't?

Most likely, your domain records have already been updated by the provider to which they are connected. Within 72 hours, these records will also be updated with your provider.

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

What is a DNS server

A DNS server is a server that allows you to convert 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

The DNS service is used to map a domain name to an IP address. The DNS system consists of many servers at 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, you typed the website address in the address bar of your browser;
• If the local DNS contains this entry, then it gives the answer. In our example, the browser will receive the IP address of the site and contact it.
• If the local DNS does not have the required entry, then it contacts the next DNS server, and so on, until the entry is found.

One IP address can be associated with many domain names - this is called virtual hosting. But one domain name can be assigned multiple IP addresses, usually to distribute the load.

DNS Server Records

The DNS server has several types of records, let's look at 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 a SOA record, which will indicate on which server the information about this domain is stored. The SOA record has several parameters:

1. Serial - serial number of the zone. It increases every time changes are made in a given domain; this is necessary to detect changes from the secondary DNS server and determine the need to update its 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 necessary.
3. Retry - repeat the update. Sets the frequency of attempts to update the secondary DNS when connecting to the primary fails. Set in seconds.
4. Expire - the period for storing 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 given zone record on secondary servers. If the data changes frequently, it is recommended to set the value to a small value.

NS entry(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

An additional digit in front of mail.example.com indicates the priority value - a smaller digit means a higher priority.

PTR Record(Pointer) - is the reverse of the A record. Searching for an IP address by domain is carried out using the A record, and searching for a domain by IP address is carried out using PTR records. It makes sense to set PTR records only on physical hosting, since on virtual hosting all names have the same IP.

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

Full 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)