Dns record types. Creating your own NS records
DNS (Domain Name System) is the "phone book" of the Internet. It uses the IP address as the phone number, and domains as the contact names. Such a book can include not only “ telephone number", but also Additional information about the contact ("e-mail", "place of work", etc.).
Domain information is stored on DNS servers. To add it to the DNS system, you need to register resource records... With their help, servers share information about domains with other servers. Until resource records for the domain are registered, it is not in " phone book»The Internet. Therefore, the work of the site or mail on it is impossible. Before you start specifying resource records, you need to delegate a domain, that is, register DNS servers for it. You can do it according to the instructions:. Then go to resource records. The changes will take effect after the DNS servers are updated (usually before 24 hours).
The main resource records are A, CNAME, MX, TXT, and SPF records. Let's consider them in more detail.
Record A
The A (address) record is one of the key resource records on the Internet. It is needed to connect the domain with the server IP address. Until an A-record is registered, your site will not work.
When you enter the site name in address bar browser, namely by DNS A records determines from which server you want to open your site.
Examples of A record:
| Record name | Record type | Meaning |
|---|---|---|
| site.ru | A | 123.123.123.123 |
| shop.site.ru | A | 123.123.123.123 |
You can register an A-record according to the instructions:
CNAME record
CNAME (Canonical name) is a record that is responsible for linking subdomains (for example, www.site.ru) to the canonical domain name (site.ru) or another domain.
The main function of CNAME is to duplicate domain resource records (A, MX, TXT) for different subdomains.
Examples of CNAME record:
| Record name | Record type | Meaning |
|---|---|---|
| www.site.ru | CNAME | site.ru |
| webmail.site.ru | CNAME | webmail.hosting.site |
If you register CNAME for a subdomain www.site.ru and specify the value of site.ru, the site will open from the same IP address as site.ru... If you register CNAME for mail.site.ru and indicate the value webmail.hosting.site then on mail.hosting.site the same resource records will be distributed as for the webmail.hosting.site.
Using a CNAME record excludes the use of other resource records for this subdomain, that is, for the subdomain webmail.site.ru or www.site.ru you cannot add both an A record and a CNAME record at the same time.
You can register a CNAME record according to the instructions:
MX record
MX (Mail Exchanger) - a record responsible for the server through which mail will work. MX records are critical to how mail works. Thanks to them, the sending side "understands" to which server you need to send mail for your domain.
Examples of MX records:
| Record name | Record type | A priority | Meaning |
|---|---|---|---|
| site.ru | MX | 10 | mx1.hosting.site |
| site.ru | MX | 15 | mx2.hosting.site |
where mx1.hosting ..
Usually, two mail servers are specified so that if one of them is unavailable, mail will still be sent to the other. The priority of the entry determines which server the mail should be sent to first. The lower the number, the higher the priority. Thus, for the domain name site.ru, the mail server is mx1.hosting..hosting .. If the priority is the same, the server is selected at random.
You can register an MX record according to the instructions:
TXT record
TXT (Text string) - a record used to set the required text comments for the domain. Often used for domain ownership checks when connecting additional services as well as a container for the SPF record and DKIM key. You can register an unlimited number of TXT records if they do not conflict with each other.
You can register a TXT record according to the instructions:
SPF record
The SPF record (Sender Policy Framework) contains information about the list of servers that are allowed to send messages on behalf of the specified domain. Avoids unauthorized use. The SPF setting is written in the TXT record for the domain.
An example of an SPF record:
| Record name | Record type | Meaning |
|---|---|---|
| site.ru | TXT | v = spf1 include: _spf.hosting..123.123.123 a mx ~ all |
where 123.123.123.123 is the IP address of the server you need.
In this example:
- v = spf1- defines the version of the used SPF record;
- include: _spf.hosting.site- includes in the SPF record the value of the SPF record of another domain. That is, all values of the SPF record for the "_spf.hosting.site" domain will be valid for the domain;
- ip4: 123.123.123.123 - allows receiving mail from the IP address 123.123.123.123;
- a- allows receiving mail from the server, the IP-address of which is in the domain's resource A-record. Simply put, from the server where the site is hosted;
- mx- allows receiving mail if the sending server is specified in one of the MX records for the domain;
- ~ all- if the letter came from a server that is not included in the above list, it should be analyzed more carefully. Also sometimes used -all- in this case, the letter does not pass additional checks and is immediately rejected.
You can register an SPF record according to the instructions:
NS, PTR, SOA records are service records and, as a rule, are automatically configured.
NS record
The NS (Authoritative name server) record points to the DNS servers that are responsible for storing the rest of the domain's resource records. The number of NS records must strictly correspond to the number of all servers serving it. Critical to the operation of the DNS service.
PTR record
PTR is a reverse DNS record that associates a server's IP address with its canonical name (domain). The PTR record is used to filter mail. If you have ordered a VPS or Dedicated server, you can register a PTR record according to the instructions:
SOA record
SOA (Start of Authority) - The initial zone record that indicates which server stores the reference domain name information. Critical to the operation of the DNS service. You can learn more about what an SOA record is and how to check it.
On the page DNS zones a list of zones that you can edit is presented (the changes you made will be updated on our server within 30-40 minutes, however, how soon it will be noticeable to users depends on the settings of the Internet provider's server through which the connection to the network is made ). When you click on the zone name (let in our example it will be domain.tld) the DNS editor page opens. Let's take a look at each of the fields on this page separately.
- @ — the "@" symbol means that the action of the recording will apply to the zone on the edit page of which you are. In our case, it is domain.tld.
- abc - a set of letters and numbers ("abc" was chosen as an example - you can enter your name) means that the record will apply to the zone more low level than the one you're on the edit page you're on. In our example, the record action will apply to the zone abc.domain.tld.
- * — the symbol "*" means that the record will apply to all variants of zones below the one on the edit page of which you are. In our case, it is 123.domain.tld, abc.domain.tld, qwe.rty.domain.tld etc.
In the field "type" you are presented with several options. Let's consider each of them separately:
- A - is used to match a hostname to an IP address.
- MX - used to indicate mail server for the domain.
- CNAME - used to redirect a hostname to another name.
- SRV - used to indicate a server providing services for a particular service. In a rough approximation, this is analogous to an MX record, which indicates where email should be delivered that is addressed to a specific domain. Supported by such protocols as XMPP (Jabber), SIP, LDAP. By using this type of record, you can host the Jabber server on a separate machine, rather than on the same machine as the DNS A record points to.
- TXT - is used to specify additional text information that the domain owner wants to communicate.
- Field "MX preference" available for filling only in the case of creating / editing records of the MX type. The numerical value specified in this field determines the priority of using the mail server. Since several mail servers can be specified for one domain, the order in which attempts to deliver a letter to these servers will be carried out is determined by the priority of the corresponding MX record. The lower the number in the “MX preference” field, the higher the priority of the server itself.
Value (IP / host.) Field is filled in depending on the selected entry:
- For A records the IP address is indicated.
- For MX records the name of the mail server is indicated. If you write the name in full, be sure to put a full stop at the end!
- For CNAME records specifies the name of the host to which we set the redirection. There must be a period at the end of the name!
- For SRV records a string of the form "priority weight port value" is indicated, where priority, weight and port should consist only of numbers, and the value - full name host with a dot at the end.
- For TXT records an arbitrary text string... Restriction - a record can only consist of letters of the Latin alphabet, numbers, spaces and the following symbols:. ,; : - = "/ ~?
Name field suggests several options for filling:
Generic DNS records
Let's consider some of the most popular situations:
A-record: it is necessary for the site to be opened from another server
If it needs to be done
- @ IN A<серверы.masterhost>
- name: @
- type: A
- If it needs to be done for the subdomain of the domain specified in the "DNS zones" section
- abc.domain.tld in the domain zone domain.tld.
- type: A
- value (ip / host.): server IP address
MX record: it is necessary for domain mail to be served by another server
- name: mail-server
- type: A
- value (IP / host.): IP address of the mail server
If you want to change the mail server for the domain specified in the "DNS zones" section, click on it with the mouse and, if on new page there is a record:
- @ IN MX 10<серверы.masterhost>
turn it off. After the record is disabled, click on the "add new record" link and create a record like this:
- name: @
- type: MX
- @ IN MX 10<серверы.masterhost>
- If you want to change the mail server for subdomain of the domain specified in the "DNS zones" section, click on the domain name with the mouse, and add a new record with the following parameters:
- name: abc ("abc" is given as an example. Works if you want to create an entry for a domain abc.domain.tld in the domain zone domain.tld. In your case, there will be some other name)
- type: MX
- MX preference: numeric value, let's say 10.
- value (IP / host.): mail-server
if you unknown server name, but you know its IP address - you must first create a new record in the domain zone with following parameters:
SRV record
To make an SRV record, you need to obtain the following information from the owner of the service:
- Service
- Protocol (proto)
- Priority
- Weight
- Port (port)
- Server (target)
* TTL does not change, so you do not need to specify it;
The record name is formed from the service name and protocol: _service._protocol
The entry value has the following format: priority weight port server.(there must be a period at the end of the name!)
List of NS servers of the subdomain
If the main domain is delegated to the masterhost servers, then the NS-servers of the third-level subdomain are changed through the editor.
If the main domain is supported on third-party servers, then the list of NS servers for its subdomains is changed in the control panel of these servers.
PTR record: you have allocated an IP address to me and I want to map that IP address to a specific hostname
To do this, go to the section DNS zones, select your IP address and click on the button «>>» ... In the field available for editing, enter the hostname with a dot at the end and click "save".
SPF record
A fairly common technique used by the organizers of SPAM mailings is to fake the return address of the letter. In this case, bounce messages may sometimes be sent to your mailboxes, if one or more of these SPAM messages with the return address of your mailbox were blocked by recipient servers.
There are several technologies to help protect your mail domain from being used by intruders: SPF, DKIM, DMARC
V this moment our mail servers support SPF and DKIM technologies. If sending mail on behalf of your domain addresses is carried out only from our mail servers, we recommend adding the following TXT record to the DNS zone of this domain with our SPF rule, which will not allow your domain to be used on third-party mail servers.
- name: @
- type: TXT
- value: v = spf1 include: _spf.site -all
This rule will force recipient servers to block all SPAM messages that use your domain name as sender addresses. ...
Dear users, we kindly ask you to be especially careful when editing DNS zones, incorrect configuration of the DNS zone can lead to the inoperability of your resources for a sufficient long term!
DKIM
To protect against fraudulent activities on behalf of your domain, we recommend adding a DKIM record to the DNS zone. If you use our mail, you can add DKIM in your Personal Account.
Using this entry, you can specify certification authorities who are authorized to issue SSL / TLS certificates for this domain. A CAA record helps prevent unauthorized issuance of certificates by mistake or for fraudulent purposes.
This is just an example, the exact information on the content of the "Value" field should be checked with your certification authority.
Modifying domain NS servers
To change the list of DNS servers:
- Go to ;
- Specify login cXXXXX and password;
- Open the section " General services"And click" change "opposite desired domain;
- Click on the link "Change delegation settings";
- To indicate third party servers, select "Delegate to third-party servers";
- Enter the DNS server addresses, one per line;
- To cancel preliminary testing of DNS servers, check the "No testing" property;
- Click the Save button.
If login cXXXXX and the password for access to the Personal Account are lost, then you can use the link to restore the access details.
Important:
- Changing the list of DNS servers is possible only after the completion of mobile authorization.
- From the moment of domain delegation (changing its list of NS-servers), it will take from 6 to 72 hours before it will be available on the Internet.
Webmin does not support all record types that BIND knows. The work is supported only with those that are more common. Below will be described the types of records that Webmin is able to work with. In addition, will be given a brief description of each of these types.
Record types available in the direct zone:
Address (A)- address type of record. This type associates an IP address with a hostname. Any system that you want to connect to via HTTP, telnet, or another protocol that has a hostname assigned to it must have an address record so that the hostname can be retrieved from the hostname. Remember, one hostname ( hostname) can have multiple address records (records A type). This is often used to distribute the load on a website across multiple systems. In addition, it is possible to create several address records with different hostname (hostname), but the same IP address, as if created name-based) virtual servers Apache.
When creating or editing an address record, the field Address (IP address) is for recording the IP address that will be associated with hostname. Field Update reverse??) , is responsible for automatic creation and change the entry Reverse Address, type ofPTR) v Reverse zone) ... See Adding and Editing Records, for details.
Name Server (NS)- record type defining the name of the server responsible for maintaining the zone. Each zone must have at least one NS record and, in addition, may have additional NS records for subdomains of this zone. If you are setting up an additional (second, secondary) DNS server for a certain zone, do not forget to check if an NS record has been added for this zone on the main (primary, master) DNS server. In this case (if you configure additional DNS server), the record name must be canonical for the zone, e.g. example.com (i.e. completely with the parent zone (s)).
When creating or editing a record of this type, the Name Server field is used to enter the IP address or hostname of the DNS server responsible for maintaining the zone. If you enter hostname, you also need an Address record (A-record) with the IP address for this hostname, located in a certain zone, on your DNS server.
Name Alias (CNAME)- this type of record allows you to create aliases (aliases, links, bindings) to already existing address (Address; type A) and reverse address (Reverse Address, type PTR) records. When a DNS client requests an IP address of this type (Name Alias), it receives the IP address specified in the record to which the binding is made. This can be useful if you want a particular host to be reachable under multiple names. Of course, this can be achieved by creating several address records, but the option with aliases is more convenient in that if some host has changed the IP address, then there is no need to change something in the aliases. Whereas, if you use a lot of address records, you will have to make changes to each record associated with this some server.
The form for creating and editing the Name Alias record contains the Real Name field for entering the canonical real name the record to which the alias will point (for example, webserver.example.com).
Mail Server (MX)- the type of record that reports mail programs, like Sendmail or Qmail, where the mail server is located (the server to which you need to contact to deliver mail in this domain). Without this record, mail for this domain will be delivered to the system (the server, host), whose IP address is indicated in the address record (Address, type A) for this zone.
Each MX record has priority, which allows offloading the load between multiple mail servers. Accordingly, the priority tells the mail programs (delivery providers) which of the servers will be addressed first. And then in descending order, for example, if a server with a high priority does not respond.
Note: High priority in this context does not mean the most big number, and the smallest, i.e. 10 is higher than 50.
Low MX priority servers are designed to forward mail to some host that stores mail. Then, when the highest priority mail server becomes free, it will take letters from storage and send them to the address.
When adding or editing an MX record, two fields are available to you. In the first, you need to enter the canonical hostname (hostname) or a link to it (to the hostname) of the mail server. The second field is for entering the priority of the MX record. Usually, the priority for the main server is set to 5. If you have only one mail server, then the priority does not matter. In addition, you can set the same priority for two mail servers. In this case, the server that will deliver the letter to the addressee will be randomly determined.
Host Information (HINFO)- the type of record used to store information about the architecture and operating system of a host. For example, you may need to create an entry for the test.example.ru server that it (the server) is an x86 PC running FreeBSD. However, this is very rarely used, since such information can be used by cybercriminals when preparing attacks.
When adding or editing this type of record, the Hardware and Operating System fields are for entering the architecture and operating system host, respectively. You should enter data in these fields without spaces, replacing the spaces with the "earth" sign, that is, "_" without quotes.
Text (TXT) - a record type that associates arbitrary text information with the selected zone (domain). That is, you cannot add TXT record just somewhere. It can only be added when editing a certain zone. So this will be attached to the editable zone. text information... This type can be used to attach comments to a certain zone (domain). Be careful, as this information can be read by anyone who has requested information about the zone (domain), so do not place confidential information in the comments.
When adding or editing this type of record, the Message field is for entering a comment on the host. This text can contain spaces as well.
Well Known Service (WKS) - an entry type that associates the hostname, port, and protocol of some service (eg mail) with the selected zone. This can be used, for example, to tell clients which host is the mail server. However, most programs do not ask for WKS records, so in practice this type of record is often useless.
When adding or editing this type of record, the Address (IP address), Protocol (Protocol) and Services (Services) fields are intended to enter the IP address of the host of some service that is provided for this zone (domain); network protocol used by the service - TCP or UDP; port number on which it is provided this service, respectively.
Responsible Person (RP)- the type of record that associates a person or a group of people responsible for this zone (domain). The E-mail address and Text Record Name fields are for E-mail input the address of the person in charge and his name (first and last name), respectively. This type of record is rarely used.
Location (LOC)- the type of record used to indicate the physical location of the host. In latitude and longitude coordinates. May be useful for large organizations, servers that are in different countries.
When adding or editing this type of record, the Latitude and Longtitude field is for entering latitude and longitude. For example, for host cambridge-net.kei.com there is 42 21 54 N 71 06 18 W -24m 30m.
Service Address (SRV)- a type of record that associates a domain name, service name and protocol with some host. In other words, this record is used to indicate the location of a certain service on a certain host. For example, this post type can be used if you want to indicate that the POP3 server for example.com is mail.example.ru and the web server is www.example.ru.
When adding or editing this type of record, the Protocol and Service Name fields are used to enter the protocol that the service uses (TCP, UDP, TLS) and the name (name) of the service (this name can be taken from the file / etc / services) respectively. Service names can be like pop3, telnet and others. When a client is looking for some SRV record, the record request is as follows: _telnet._tcp.example.ru (For example, it can be like this). Webmin will automatically convert your created entry to this (correct) view. This means that there is no need to manually create or edit this type of record.
The Priority field is for entering the priority for this server, meaning (priority) is the same as the priority for MX records. The Weight field is for entering a number representing the “weight” of this host. Users' requests will mainly be directed to the server with greater "weight".
The Port field is intended for entering the port number on which this service is provided.
Public Key (KEY)- the type of record that associates a "key" to some host. This key is used for IPsec VPN.
Record types available in the reverse zone:
Reverse Address (PTR)- the type of entry that associates hostname with the IP address in the reverse zone. For DNS clients, you need to look for hostnames at the given IP address. You should create one record of this type for each host. However, in most cases this can be automated. Webmin can add an address entry to the reverse zone immediately after the corresponding address entry is added to the forward zone. That is, Webmin is able to synchronize the forward and reverse zones.
When adding or editing this type of record, the Address and Hostname fields are for entering the IP address (For example, 192.168.1.5; This address will be automatically converted by Webmin to the in-addr.arpa format used by DNS server for the reverse zone) and hostname (hostname) in canonical form (for example, test.example.ru . ), respectively.
CAUTION: When entering Hostname, be sure to end with a period. This is not a typo.
Name Server (NS)- the NS record type in the reverse zone is intended for the same as in the direct one - it informs others DNS servers, IP address or hostname (hostname) of the server serving some zone (domain) or some subdomain.
The Zone Name field is used to enter the name of the zone that this server serves. Usually the name of the zone is the same as the name of the zone to which this entry is added. In this field, you should enter a value in the format in-addr.arpa (Since there is no synchronization, as in the address records - type A and PTR). Therefore, the view of the Zone Name for 192.168.1 will look like 1.168.192.in-addr.arpa . (Period is required at the end, this is not a typo) In the Name Server field, you must enter the IP address or hostname in canonical form (eg ns1.example.ru).
Name Alias (CNAME)- the type of record in the reverse zone, intended for the same as in the direct one - alias, link, binding to some record. For the Name and Real Name fields, you must enter a value in the in-addr.arpa format, as Webmin does not do this automatically.
Account addresses (A) Account A displays the computer name as a numeric IP address. In other words, this entry indicates the hostname and IP address a specific computer to match the hostname to a specific IP address. This is the record that name server A must send to another name server and receive a response to the request. Below is an example of what an A record should look like:
peter.gudzondns.com. IN A 36.36.1.6 The first column contains the hostname of the computer. The second column list is the record class. For basic DNS operation, you only need the IN designation set for the Internet. The next column denotes the type of entry, and the last column is the actual IP address. It is possible to add more than one IP address for a given hostname. This is necessary when a firewall is used and there are two ethernet cards on the same computer. All you have to do is add a second A record, filling in the same columns except for the IP address. It is also possible to display more than one hostname for one IP address. However, this is not recommended because DNS has a special record that allows computers to have aliases called a CNAME record.
In-addr.arpa PTR records are the exact opposite of A. records. They allow your computer to be recognized by its IP address. This is called "reverse lookup". It is increasingly used when a computer does a reverse lookup on your computer before accessing services (for example, pages on the WWW). Reverse lookup is a good security measure for your computer, as it verifies that your computer is exactly what it should be. The In-addr.arpa entry looks like this: 6.1.36.36.in-addr.arpa. IN PTR peter.gudzondns.com. As you can see from the example for record A, at the beginning of this record there is an inverse IP address for the hostname in the last column.
The first column contains the domain for which this record starts permissions. The next two pieces of information should look familiar. The "draven.gudzondns.com" entry is the primary name server for the domain. The last entry in this column is valid email address if you replaced "@" for the first ".". It must always be a valid contact address for the SOA record. The following data is slightly different from what we have already used. Serial is a record of how often this DNS record can be changed. Every time a change is made, Serial must be incremented. Other nameservers that retrieve zone information from the primary only retrieve the zone if Serial in the primary nameserver record is higher than Serial in that record. Thus, the name servers for the domain can change themselves. It is recommended to use your Serial in the YYYYMMDDNN format, where NN is the day the DNS was changed. Everything numerical values recording time is made in seconds. The Refresh number indicates how often the secondary nameserver should check the primary for changes to Serial. "Retry" is how long the secondary server should wait before trying to reconnect to the primary server if the connection was lost. "Expire" how much the secondary server should use its current record when it fails to recover, and “Minimum” means how much your nameservers should cache or keep this record.
Domain Name System (DNS) is a distributed database that stores information about domains: domain ip-addresses, ns-servers serving the domain, mx-records for this domain and other service information.
Domain information is stored as records. Basic post types:
1.SOA record- contains the name of the primary ns-server for this zone, the e-mail of the administrator of this zone, serial number, the default cache time values for all zone records.
To create an SOA record (raising zones to a domain), you need to add a domain through the "Domain transfer" section in personal account.
2. NS record indicates the DNS server for this domain. For example, our NS records:
ns1.site
ns2.site
ns3.site
Through the hosting control panel in your personal account, you can set / change NS records only for subdomains. You can change NS records for the main domain through the registrar or upon request to "Online Support".
3. A and CNAME records.
The A record associates a hostname with an ip address.
A CNAME record or canonical name record is used to redirect to another name.
Both of these records can be changed in the hosting control panel in the DNS - Alias section. When setting / changing the A - record, the IP address is entered in the "Address" field;
Example: 217.112.XX.XX
When setting / modifying a CNAME record, the canonical name with a dot at the end.
Example: test.example.ru.
4. MX record
Indicates servers that accept mail for this domain. An MX record consists of two pieces of data: priority (the lower the number, the higher the priority) and the domain name (mail server).
You can also change this record in the DNS (MX) section. Domain name in the "Address" field it is always written with a dot at the end.
For example: mail.example.ru.
5.SRV and TXT records.
SRV records indicate server locations for various services.
An SRV record consists of the following parts:
Service._proto.name TTL class SRV priority weight port target
service is the name of the service. For example xmpp or sip.
proto is the name of the protocol. Usually tcp or udp.
name is the name of the domain in which this service is hosted.
class - DNS standard, class field
TTL - DNS standard, time to live.
priority - priority of the entry. The lower the number, the higher the priority
weight - weight of the entry. Used for entries with the same priority
port - the port that hosts the specified service on this server
hostname (target) - server name.
TXT records are used to indicate additional text information.
You can add and change SRV-, TXT-records in the DNS (SRV, TXT) section of the hosting control panel.
6. PTR record
Binds the IP of a host to its canonical name.
Used to reduce the volume of unwanted mail. Many secondary servers Email check for the presence of a PTR record for the host from which the message is being sent. In this case, the PTR record for the IP address must match the name of the sending mail server, which it represents during the SMTP session.
Configured on the side of the ISP that provided the IP address.
All changes to DNS settings made in your control panel will be effective only for domains delegated to our NS-servers.
If any records are changed for the main domain, for example, example.ru, then the "Name" field must be left blank, if any value is entered, for example 1, then the settings will be applied to the 1.example.ru subdomain