Record type a dns. What happens when you change DNS records
Webmin does not support all record types that BIND knows. Only those that are more common are supported. Below we will describe the types of records that Webmin can work with. In addition, it will be given a brief description of each of these types.
Post types available in the direct zone:
Address (A)- address type of record. This type associates an IP address with a hostname. Any system to which you want to connect via HTTP, telnet or other protocol that has a hostname assigned to it must have an address record so that the hostname can be used to find the host's IP address. Remember, one hostname( hostname) may have several address records(records A type). This is often used to distribute the load of a website across multiple systems. In addition, you can create multiple address entries with different hostnames, but the same IP address, as if you were creating name-based) virtual servers Apache.
When creating or editing an address entry, the field Address(IP address) is intended to record the IP address that will be associated with the hostname. Field Update reverse??) , is responsible for automatic creation and changing the entry Reverse Address, typePTR) V Reverse zone) . See Adding and Editing Entries for details.
Name Server (NS)- record type defining the name of the server responsible for servicing the zone. Each zone must have at least one NS record and may also have additional NS records for subdomains of that zone. If you are setting up a secondary DNS server for a certain zone, then do not forget to check whether the NS record for this zone has been added to the main DNS server. In this case (if you configure additional DNS server), the entry name must be canonical for the zone, for example example.com (i.e. all with the parent zone(s)) .
When creating or editing a record of this type, the Name Server field is intended for entering the IP address or hostname, the DNS server responsible for servicing the zone. If you enter a hostname, then you also need an Address record (A-record) with an 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 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 certain host to be accessible 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 a host’s IP address has changed, then there is no need to change anything in the aliases. Whereas, if you use many address records, you will have to make changes to each record associated with this certain server.
The form for creating and editing a Name Alias record contains a Real Name field intended for entering the canonical real name the record to which the alias will point (for example webserver.example.com).
Mail Server (MX)- a record type that tells email programs like Sendmail or Qmail where the mail server(the server that needs to be contacted to deliver mail in this domain). Without this record, mail for this domain will be delivered to the system (that server, host) whose IP address is indicated in the address record (Address, type A) for this zone.
Each MX record has priority, which allows you to offload the load between multiple mail servers. Accordingly, priority tells mailers (deliveries) which server will be contacted 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.
Servers with low MX priority are designed to forward mail to some host that would store mail. Then, when the mail server with the highest priority is free, it will take the letters from storage and send them to the address.
When adding or editing an MX record, you have two fields available to you. In the first one, you must enter the canonical hostname (host name) or a link to it (host name) of the mail server. The second field is intended for entering the priority of the MX record. Typically, the main server is set to priority 5. If you have only one mail server, then the priority does not matter. Additionally, you can set two mail servers to have the same priority. In this case, the server that will deliver the letter to the recipient will be determined randomly.
Host Information (HINFO)- a record type used to store information about the architecture and operating system of a certain host. For example, you may need to create an entry for the server test.example.ru that it (the server) is an x86 PC running FreeBSD. However, this is very rarely used, since such information can be used by attackers when preparing attacks.
When adding or editing this record type, the Hardware and Operating System fields are for entering the architecture and operating system host, respectively. You should enter data into these fields without spaces, replacing spaces with a ground 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 a TXT record just somewhere. It can only be added when editing a certain zone. So this text information will be attached to the edited zone. This type can be used to attach comments to a certain zone (domain). Be careful, as this information can be read by anyone requesting zone (domain) information, so do not post sensitive information in the comments.
When adding or editing this type of record, the Message field is for entering a comment to the host. This text may also contain spaces.
Well Known Service (WKS) - a record type that associates the hostname, port and protocol of some service (for example, mail) with the selected zone. This could, for example, be used to indicate to clients which host is the mail server. However, most programs do not request 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 and Services fields are intended for entering the IP address of the host of some service that is provided for this zone (domain); network protocol, which is used by the service - TCP or UDP; port number on which is provided this service, respectively.
Responsible Person (RP)- a record type that associates a person or group of people responsible for this zone (domain). The E-mail address (E-mail address) and Text Record Name (Name) fields are intended for entering Email addresses the responsible person and his name (first and last name), respectively. This type of record is rarely used.
Location (LOC)- a record type that is used to indicate the physical location of the host. In latitude and longitude coordinates. Perhaps it will be useful for large organizations, servers located in different countries.
When adding or editing this record type, the Latitude and Longtitude field is for entering latitude and longitude. Example, for the host cambridge-net.kei.com there is 42 21 54 N 71 06 18 W -24m 30m .
Service Address (SRV)- record type that associates Domain name, service name and protocol with some host. In other words, this entry is used to indicate the location of some service on some host. For example, this record type can be used if you want to indicate that the POP3 server for example.ru is mail.example.ru, and the web server is www.example.ru.
When adding or editing this record type, the Protocol and Service Name fields are for entering the protocol that the service uses (TCP, UDP, TLS) and the name(s) of the service (this name can be taken from the file / etc/services) respectively. The names of the services can be pop3, telnet and others. When a client is looking for some SRV record, the type of record request is as follows: _telnet._tcp.example.ru (For example, it could be like this). Webmin will automatically convert the entry you created to this (correct) form. This means that there is no need to create or edit this type of entry manually.
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 indicating the “weight” of this host. User requests will be predominantly to the server that has more “weight”.
The Port field is intended for entering the port number on which this service is provided.
Public Key (KEY)- a record type that associates a “key” with some host. This key is used for IPsec VPN.
Post types available in the reverse zone:
Reverse Address (PTR)- a record type that associates a hostname with an IP address in the reverse zone. For DNS clients, you need to look for hostnames at a given IP address. You should create one entry of this type for each host. However, in most cases this can be automated. Webmin can add an address record to the reverse zone immediately after the corresponding address record is added to the forward zone. That is, Webmin can synchronize the forward and reverse zones.
When adding or editing this type of record, the Address (IP address) and Hostname (Hostname) fields are intended for entering the IP address (For example, 192.168.1.5; This address will be automatically converted by Webmin into the in-addr.arpa format used by DNS server for the reverse zone) and hostname (host name) in canonical form (For example, test.example.ru . ), respectively.
ATTENTION: When entering Hostname, be sure to add a period at the end. This is not a typo.
Name Server (NS)- the NS record type in the reverse zone is intended for the same thing as in the forward zone - it tells other DNS servers the IP address or hostname (hostname) of the server serving a certain zone (domain) or some subdomain.
The Zone Name field is intended for entering the name of the zone that this server serves. Typically, 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 address records - type A and PTR). Therefore, the Zone Name for 192.168.1 will look like 1.168.192.in-addr.arpa . (The 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 (for example, ns1.example.ru).
Name Alias (CNAME)- a record type in the reverse zone, intended for the same thing as in the forward zone - alias, link, binding to some record. In the Name and Real Name fields, you should enter the value in the in-addr.arpa format, since Webmin does not do this automatically.
Any Internet user who has domains on the servers of hosting providers can create and edit their DNS records. DNS records have a Name, Record Type and Address. These names may change in different panels. For example, it could be like this:
Name/Host/Alias; Record type; Meaning/Answer/Destination/Address.
In all options, the “Record Type” remains the same.
Entry name
The record name, also known as host/alias, is the domain name to which the record being created belongs or is associated.
When creating an entry, the domain name is indicated in full in the “Name” field. The subdomain or alias name does not need to be specified in full. It is enough to indicate the third level name: mail, www, ftp. If you enter full name, be sure to put a period at the end. That is, the name mail and mail.example.ru. is the same name in the Name/Host/Alias field.
DNS record types
Let's look at the main types of DNS records that you will encounter when servicing your domains.
Record Type A
Record type: A (address record) or (Internet 4 address). This type of record associates a specific domain name with a specific, precise IP address.
You can add more than one IP address for one domain (hostname). This is necessary if a firewall is used. To do this, you need to add a second record of type A, similar to the first. By specifying only a different IP.
In theory, you can specify more than one domain for one IP address. But this is not necessary, since the Domain Name System (DNS) has a record specifically designed for creating aliases. This record type is called CNAME.
Record type AAAA
Record type: AAAA (address record for IPv6) or (Internet 6 address). Same. Same as record type A, but the IP address has appearance via IPv6 protocol. For example: IPv6-2a03:4900:0:3::99:155
CNAME record type
CNAME (canonical name record). A CNAME record allows you to have and use more than one domain name (host) on a server.
First, one type A record is created for one IP address. The domain name in the Type A record is called the canonical name. Other domains are called mnemonic. Mnemonic names can be aliases (arbitrary names) or subdomains. Here's an example CNAME record:
popov.example.ru. CNAME example.ru.(don't forget the dots at the end).
A server can have any number of aliases. For each alias, you need to create a CNAME record.
Another example of a CNAME record:
hosting-1 IN A 8.8.8.8
www IN CNAME hosting-1
ftp IN CNAME hosting-1
We buy a second IP and transfer the ftp subdomain to the second IP:
hosting-1 IN A 8.8.8.8
hosting-2 IN A 8.8.8.9
www IN CNAME hosting-a
ftp IN CNAME hosting-b , transfer to a second hosting FTP server.
Another example of a CNAME record:
hosting-1 IN A 8.8.8.8
peter IN CNAME hosting-1
oleg IN CNAME hosting-1
We associate aliases with the following CNAME records:
example.com. IN CNAME example.ru.
www.example.com. IN CNAME example.ru.
test.example.com. IN CNAME example.ru.
Thus, we link the domains example.com, www.example.com, test.example.com with the canonical domain example.ru. The periods at the end are required.
Another example of redirection using a CNAME record
www.example.ru. IN CNAME example.ru.
Typically, servers by default create CNAME records only for subdomains of the main domain and do not create them for other domains (as in the photo).
MX record type
MX (mail server). This entry creates a subdomain that is served by an internal (its own) mail server.
For example: Name/host/alias - example.ru; Record type -MX (mail server); Meaning/answer/destination/Address – mail. With this entry you create a mail subdomain mail.example.ru. If you are using the internal mail service of the server, then you need to create a record type “A” for the mail.example.ru subdomain. Name: mail - A (record type) - Address: server IP.
You can use third-party mail servers as a mail service. To do this, you need to link your domain to a third-party mail server. It will automatically create an MX record for you. If they don’t create it, they will give you the address of the mail server. After that, you need to create CNAME and MX records on your server.
Redirect with CNAME record mail domain mail.example.ru. to the email domain address. And an MX record for the domain example.ru itself. set the address of your third party mailbox. As an example, you can use the Yandex mail server.
- For Yandex, the MX record type will be like this:
Name/host/alias - example.ru; Record type -MX (mail server); Meaning/answer/purpose/Address – mx.yandex.ru. Priority 10.
- The CNAME type is:
Name/host/alias – mail; Record type –CNAME; Meaning/response/destination/Address –domain.mail.yandex.ru. Priority 10.
On the Yandex mail server, without domain delegation, you can connect it only to the Yandex mail server by creating a mailbox there.
In addition to Yandex, using MX records you can link a domain to email Google servers, Mail.ru and others:
Record type NS
Record type NS (name server). This is perhaps the most important type records. It determines the domains (addresses) of DNS servers serving this domain.
Record type TXT
TXT (text entry). This is an informational entry. It does not carry a functional load.
Record type SOA (Start Of Authority)
SOA record type shows where the basic information about this domain is stored on which server. The SOA record type specifies the fully qualified domain name of the zone. The qualified domain name must end with a period. An SOA record may have an @ symbol instead of a qualified name. In this case, the domain name will be taken from the configuration file.
- Arbitrary serial number data versions (Serial). When a secondary server requests a data update, it first checks the serial number;
- The frequency of the request for updating data from the secondary (Secondary) server (Refresh), in seconds;
- The period for re-requesting the secondary server in case of primary failure (Retry);
- Data expiration date (Expire), otherwise the expiration of time after which the secondary server will stop servicing requests if it fails to restore communication with the primary server, in seconds;
- And lastly, the time to live of DNS zone data in the cache of the server that requested it, in seconds.
Here's an example of a SOA record for Microsoft DNS
How to edit DNS records in the ISPManager panel
In the ISPManager DNS panel, records are edited on the tab: Domain names→ “Click” on a domain.
How to edit DNS records in the DirectAdmin panel
In the DirectAdmin DNS panel, records are edited on the tab: DNS Management.
The 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 in the form of records. Main 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, cache time values for all default zone entries.
To create an SOA record (raising zones to a domain), you need to add a domain through the “Domain Transfer” section in your personal account.
2. NS record points to 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.
An A record associates a host name with an IP address.
The CNAME record or canonical record of a name 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 an A record, the IP address is entered in the “Address” field;
Example: 217.112.ХХ.ХХ
When setting/changing a CNAME record, the canonical name with a dot at the end.
Example: test.example.ru.
4. MX record
Points to 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 entry in the DNS (MX) section. The domain name in the “Address” field is always written with a dot at the end.
For example: mail.example.ru.
5.SRV and TXT records.
SRV records indicate the location of servers for various services.
An SRV record consists of the following parts:
Service._proto.name TTL class SRV priority weight port target
service - service name. For example xmpp or sip.
proto - protocol name. Usually tcp or udp.
name - the name of the domain in which this service is located.
class - DNS standard, class field
TTL - DNS standard, time to live.
priority - record priority. The lower the number, the higher the priority
weight - record weight. Used for entries with the same priority
port - the port on which the specified service is located on this server
hostname(target) - server name.
TXT records are used to indicate additional text information.
You can add and change SRV and TXT records in the DNS (SRV, TXT) section of the hosting control panel.
6. PTR record
Associates a host's IP with its canonical name.
Used to reduce the volume of unwanted mail. Many receiving email servers check for a PTR record for the host from which the email is sent. In this case, the PTR record for the IP address must match the name of the sending mail server to which it is presented during the SMTP session.
Configured on the side of the Internet provider that provided the IP address.
All changes to DNS settings made in your control panel will only be valid for domains delegated to our NS servers.
If any records change for the main domain, for example example.ru, then the “Name” field must be left empty; if any value is entered, for example 1, then the settings will be applied to the subdomain 1.example.ru
On the page DNS zones a list of zones that you can edit is presented (the changes you make will be updated on our server within 30-40 minutes, but how quickly this will be noticeable to users directly depends on the settings of the Internet provider server through which you connect to the network ). When you click on the zone name (let it be in our example domain.tld) the DNS editor page opens. Let's look at each of the fields presented on this page separately.
- @ — the “@” symbol means that the entry will apply to the zone on which you are on the editing page. In our case, this is domain.tld.
- abc - a set of letters and numbers ("abc" was chosen as an example - you can enter your name) means that the entry will apply to a zone at a lower level than the one you are on the edit page. In our example, the recording action will apply to the zone abc.domain.tld.
- * — the “*” symbol means that the recording will apply to all zone options below the one you are on the editing page. In our case, this is 123.domain.tld, abc.domain.tld, qwe.rty.domain.tld etc.
In the "type" field you are offered several options. Let's look at each of them separately:
- A— used to indicate the mapping of a hostname to an IP address.
- MX - used to specify the mail server for a domain.
- CNAME - used to redirect a hostname to another name.
- SRV - used to specify the server that provides the services of a particular service. Roughly speaking, this is analogous to an MX record, which specifies where the Email, which is addressed to a specific domain. Standardly 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, and not on the same machine that the DNS A record points to.
- TXT - used to indicate additional textual information that the domain owner wants to communicate.
- "MX preference" field available for filling only in case of creating/editing MX type records. Specified in this field numeric value determines the priority of using the mail server. Since several mail servers can be specified for one domain, the sequence in which attempts will be made to deliver a letter to these servers is determined precisely 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.
Field "value (IP/host.)" is filled in depending on the selected entry:
- For A-records 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 period at the end!
- For CNAME records indicates the host name 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 must consist only of numbers, and the value is the full host name with a dot at the end.
- For TXT records an arbitrary text string is specified. Restriction - the entry can only consist of letters of the Latin alphabet, numbers, spaces and the following symbols: . , ; : - = " / ~ ?
Field "name" suggests several filling options:
Representative DNS records
Let's look at a few of the most popular situations:
A-record: it is necessary that the site opens from another server
If it needs to be done
- @ IN A<серверы.masterhost>
- Name: @
- type: A
- If it needs to be done for a 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: Domain mail needs 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 new page there is an entry:
- @ IN MX 10<серверы.masterhost>
turn it off. After the entry is disabled, click on the “add new entry” link and create an entry like:
- 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 entry 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, say 10.
- value (IP/host.): mail-server
if you the server name is unknown, but you know its IP address - you must first create in the domain zone new entry with the following parameters:
SRV record
To make an SRV record, you must obtain the following data from the service owner:
- Service
- Protocol
- Priority
- Weight
- Port
- Server (target)
* TTL does not change, so it is not necessary to specify it;
The entry 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 dot at the end of the name!)
List of subdomain NS servers
If the main domain is delegated to the masterhost servers, then changing the NS servers of the third-level subdomain is done through the editor.
If the main domain is supported on third-party servers, then changing the list of NS servers for its subdomains is done in the control panel of these servers.
PTR Record: You have allocated me an IP address and I want to match that IP address to a specific hostname
To do this you need to go to the section DNS zones, select your IP address and click on the button «>>» . In the editable field, enter the host name with a dot at the end and click “save.”
SPF entry
A fairly common technique used by organizers of SPAM mailings is faking the return address of the letter. In this case, your mailboxes may sometimes receive service error messages (bounce messages), if one or more such SPAM letters with the return address of your mailbox were blocked by the recipients' servers.
There are several technologies that will help protect your email domain from being used by attackers: SPF, DKIM, DMARC
IN 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 with our SPF rule to the DNS zone of this domain, 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 emails that use your domain name as the sender address. .
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 sufficiently long time. 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 email, you can add DKIM in your Personal Account.
Using this entry, you can specify the certification authorities that have the right to issue SSL/TLS certificates for this domain. A CAA record helps prevent unauthorized issuance of certificates by mistake or fraud.
This is just an example; exact information on the contents of the “Value” field should be clarified with your certification center.
Changing domain NS servers
To change the list of DNS servers:
- Go to ;
- Specify login cXXXXX and password;
- Open section " General services" and click "change" opposite the desired domain;
- Click on the link “Change delegation settings”;
- To indicate third party servers, select “Delegate to third-party servers”;
- Enter DNS addresses servers one per line;
- To cancel preliminary testing of DNS servers, check the “No testing” property;
- Click the "Save" button.
If login cXXXXX and access password Personal account lost, you can use the link to restore your access details.
Important:
- Changing the list of DNS servers is possible only after completing mobile authorization.
- From the moment of domain delegation (changing its list of NS servers) it will take from 6 to 72 hours before it is available on the Internet.
The Domain Name System (DNS) is essentially phonebook Internet. You are dialing in address bar browser apple.com to buy accessories for the Iphone, but how does your request find Apple server with IP address 17.172.224.47? The domain name system does this for you.
If you have a small online business or blog on WordPress, then you've probably already come across setting up A and CNAME records. And if you tried to move mail from your site, then with the MX record setup. And perhaps some web service asked you to configure TXT to work with your site. Why is all this needed and what are the difficulties here?
In this article, I will describe the basics of the domain name system and the record configuration needed to work with domains.
DNS Servers
When you purchase a domain name, your registrar will typically configure it for you DNS records by default and provides DNS servers for them. Do you need DNS server(usually these are used in pairs or triplets for reliability, eg: ns1.yourregistrarserver.com, ns2.yourregistrarserver.com) to tell the directory Internet DNS Your server's IP address.
Here's a sample of my NS entries for JeffReifman.com:
All settings you specify will be configured and published online using these servers.
Now let's move on to the types of DNS records, the main one is the A record.
A records
If you type jeffreifman.com in the address bar, the request will be directed to a directory that will look for a DNS record corresponding to that root of that domain. Root in in this case means without www prefix, that is, without a subdomain, just http://jeffreifman.com. For example, a root-level A record might point to IP 107.164.32.96, so that's the address to go to.
Here's a sample A-record query on Kloth:
Subdomain records
You can also configure A records for different subdomains. For example, if you want http://www.yourwebsite.com/ to point to the same address, simply add an identical A record for the www subdomain, now the root domain and subdomain will have the same IP.
We'll be launching city-specific domains soon (portland.fleethejungle.com), which I'm hoping to host on different servers, we need the A-records of each subdomain to lead to the unique IP of the corresponding server.
Posts by wildcard
IN DNS configuration You can add Wildcard entries (using Asterisk *), allowing you to direct all subdomain traffic to a single IP. For example, if I want to place all city subdomains on one server, I will do this:
Wildcard records make it easy to link multiple subdomains to one server.
Ingress routing on the server
When traffic arrives at your server from a DNS router, you can configure how the server handles it. Here is a sample of my configuration for root and www traffic:
I also sell domains with dynamic pricing. This is how Apache handles traffic for all these domains and DNS records.
Now we will smoothly move on to CNAME records. They are useful in different cases, and especially in simplifying the management of IP addresses and migrations from one server to another.
CNAME records
A CNAME is essentially a text alias for directing domain and subdomain traffic. For example, if you were faced with setting up a service like WordPress or Tumblr, they could suggest setting up a domain using a CNAME record, and an A record with an IP.
I don't use Tumblr often, but for a while I set up my account at http://misc.jeffreifman.com/ . Here are their instructions for setting up a custom domain name - they allow you to use A records or CNAME, I chose CNAME.
Here is the DNS entry for misc. jeffreifman.com:
Misc.jeffreifman.com CNAME domains.tumblr.com.
Note: Be sure to include a dot in the CNAME address.
When a user requests misc.jeffreifman.com, DNS will send him to domains.tumblr.com, and there IP 66.6.44.4 will be found.
An important advantage of the CNAME record is that if, for example in this example, Tumblr changes its server address, you will not need to change the CNAME record. It will remain the same and Tumblr will be able to control the IP by changing the A-record to domains.tumblr.com.
I use this approach when selling domain names - most are linked to the server via a CNAME. If I need to change hosting and change server IPs, I can simply change the single subdomain A record used by the CNAME, rather than changing the A records for each domain.
Another scenario for using CNAME records is to use CNAME with CDN services as I described in the KeyCDN article. I set up cloud subdomains c1, c2, c3, c4, linking them all to the mirror at jr-faf.kxcdn.com.
What happens when you change DNS records
DNS records for the root domain and subdomains are generally independent of each other. Changing the A record of the root domain does not affect the existing CNAME address of the subdomain. However, I recently signed up for the network security service Incapsula and discovered that it requires two A records for one root domain - this can make things more complicated. In other words, you could technically have multiple A records for the same domain, which could cause conflicts.
It is also important to realize that DNS changes do not take effect immediately. When you set up DNS records for the first time (or when you change them), this data is not yet available to users. This is one of those things that makes migrating from one server to another (or changing hosting companies) difficult. In the worst case, it may take more than 36 hours.
My registrar suggested I use https://www.whatsmydns.net/ for a visual report of my DNS propagation in different areas. Below is a screenshot that I took when changing the server of my site - the changes took several hours.
The illustration below shows the DNS servers that took over my last changes:
MX Records
Now let's move on to MX records. These records tell the DNS system where to send all emails that come to you. Therefore, if I bought the domain StarWars.io and want to receive mail at [email protected], I need to do two things.
Firstly, I need to register on postal service like Google Apps or FastMail to post your mail there. Second, I need to configure the MX records so that mail goes to these servers.
For example, this is what the Google Apps configuration would look like:
Priority Mail Server 1 ASPMX.L.GOOGLE.COM. 5 ALT1.ASPMX.L.GOOGLE.COM. 5 ALT2.ASPMX.L.GOOGLE.COM. 10 ALT3.ASPMX.L.GOOGLE.COM. 10 ALT4.ASPMX.L.GOOGLE.COM.
And for FastMail like this:
In1-smtp.messagingengine.com (first, priority=10) in2-smtp.messagingengine.com (second, priority=20)
You can also use TXT records to tell spam detection servers that your mail server is only forwarding legitimate emails, as I did in the example above with the SPF record. Services like Mailgun use SPF and DKIM records when sending bulk messages.
AAAA Records
If you choose to support IPv6 addressing, you need to configure an AAAA record:
Currently, most transitions from IPv4 to IPv6 occur quietly and unnoticed. Over time, when global warming kills the last polar bear, A records will become relict records and AAAA records will become the main DNS records.