Records

This article provides information on the following topics:

• Types of supported records

  • System-defined records
  • Defining a record's hostname
• Zone apex support for CNAME records

Overview

The records associated with a zone determine how DNS queries will be resolved by our Route name servers.

Types of Supported Records

The types of records that can be associated with a zone are described below.

A record name may consist of alphanumeric characters, an at symbol (@), underscores, hyphens, and periods.

Name	Type	Common Usage	Configuration
A	Address	Maps a hostname to an IPv4 address.	Name Identifies a hostname (e.g., @ or www). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the IPv4 address that will be mapped to the specified hostname.
AAAA	Address	Maps a hostname to an IPv6 address.	Name Identifies a hostname (e.g., @ or www). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the IPv6 address that will be mapped to the specified hostname.
CAA	Certificate Authority Authorization	Defines the Certificate Authorities (CAs) that are authorized to issue certificates for the domain corresponding to this zone.	Name Identifies a hostname (e.g., @ or www). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Defines your CAA policy for the specified hostname using the following syntax: flags issue|issuewidl|iodef value Learn more (Wikipedia). Learn more (RFC 6844). Sample value: 0 issue ca.example.net
CNAME	Alias	A Canonical Name record maps a hostname to another hostname or FQDN.	Name Identifies a hostname (e.g., @ or www). Set the Name option to the @ symbol to point the CNAME record to the zone apex (e.g., example.com). Learn more. An asterisk may be used as a "starts with" wildcard. However, it may not be used in the middle or at the end of the specified value. For example, setting the Name option to * will match any hostname that ends with the zone's name (e.g., example.com), such as www.example.com or cdn.example.com. TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the hostname that will be mapped to the hostname identified by the Name option. Please append a period to this domain. If this domain does not end with a period, then the current zone's name will be appended to it. A CNAME record must point to a hostname. It should not point to another CNAME record.
MX	Mail Exchange	Maps a hostname to a mail server. Indicates the SMTP gateways to which mail can be delivered.	Name This read-only option uses the @ symbol to identify the hostname associated with the zone. TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the mail server's priority and hostname. The format for this field is: Priority Hostname. Example: 0 smtp1.example.com. Each of the above terms is defined below. Priority: Represents an integer value that defines the mail server's priority. A mail server with a lower priority value is given preference over other mail servers defined for the same zone. Hostname: Represents the mail server's hostname. The specified hostname must end with a period (e.g., example.com.).
NS	Name Server	Delegates a hostname to a name server.	Name Identifies a hostname (e.g., ns1). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the name server to which the specified hostname will be delegated.
PTR	Pointer	Maps an IPv4 address to a hostname. Use this type of record when setting up a reverse DNS lookup.	Name Identifies an IPv4 address by its fourth octet (e.g., 100). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies a hostname that will be mapped to the specified IPv4 address. The specified hostname must end with a period (e.g., example.com.).
SOA	Start of Authority	Provides authoritative information about a DNS zone.	This record is automatically defined when you create a zone and it cannot be modified.
SPF	Sender Policy Framework	Defines the mail servers that can legitimately send emails from the zone's domain.	Name Identifies the name of the zone. This option is read-only. TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the mail server's address.
SRV	Service Locator	Identifies the location of a service (e.g., FTP).	Name Identifies the name and protocol associated with the service. You may also append a hostname to this value (e.g., _http._tcp.example.com). Make sure that the name starts with an underscore (e.g., _tcp, _http, or _udp) and use a period to separate multiple protocols (e.g., _tcp._http). TTL Indicates the length of time (in seconds) that a server should cache the record. Value Identifies the service's priority, weight, port, and target. These properties should be specified as indicated below. Priority Weight Port Target Each of the above terms is defined below. Priority: An integer that defines the service's priority. A service with a lower priority value is given preference over other services with the same protocol and target. Weight: An integer that determines a service's contact order when there are other services with the same protocol, target, and priority. Port: Represents the service's port number (e.g., 80). Target: Represents the service's hostname (e.g., ftp.example.com).
TXT	Text	This record allows text to be associated with a zone. Among its many uses, it can store SPF data.	Name This field can be set to free form text. TTL Indicates the length of time (in seconds) that a server should cache the record. Value This field can be set to free form text.

System-Defined Records

Upon creating a zone, a set of system-defined records required by our DNS service are automatically added to it. These mandatory records cannot be modified or deleted. A list is provided below.

• SOA: Defines the primary name server associated with your zone.
• NS: Defines the name servers to which queries will be directed. These name servers are known as vanity name serversA vanity name server is a name server that leverages your zone name. This lends a professional appearance to a site's DNS..
• A: Defines the IP addresses (IPv4) corresponding to our vanity name servers.
• AAAA: Defines the IP addresses (IPv6) corresponding to our vanity name servers.

Although the above records are mandatory and cannot be modified or deleted, you may always add, modify, and delete, as needed, additional NS, A, and AAAA records to your zone.

Defining a Record's Hostname

Certain records (e.g., A or AAAA records) require a host label (e.g., www or us) for the Name option. Keep in mind that the origin associated with a zone (e.g., example.com) will be appended to the specified host label. For example, if you specify us as the host label in the Name option, then the hostname corresponding to that record would be us.example.com. Additional syntax information is provided below.

Points To	Syntax	Description
Origin	@	The @ symbol identifies the origin (e.g., example.com) associated with the current zone. The proper usage of this syntax is to set the Name option to the @ symbol. No other characters should be specified.
Host Label	Host Label	Specify the desired host label in the Name option. For the purposes of our DNS service, it will treat the record as if the origin (e.g., example.com) had been appended to it. Do not specify a hostname (e.g., www.example.com).

Zone Apex Support for CNAME Records

A CNAME record can be set to a zone apex (aka naked domain or root domain). This allows the zone apex (e.g., example.com) to resolve to a subdomain (e.g., www.example.com).

Configuration

Point a CNAME record to the zone apex (e.g., example.com) through the following configuration:

Setting	Value	Description
Name	@	The @ symbol indicates that the CNAME record should point to the zone apex.
TTL	Seconds	Set the TTL to the length of time (in seconds) that a DNS server should cache the record.
Value	Hostname.	The specified hostname should point to an A or AAAA record.

How Does It Work?

Our authoritative name servers resolve a CNAME record to an A or AAAA record. As a result, the hostname defined in the CNAME record will not be delivered to the requester. Rather, our authoritative name servers will serve the IP address associated with the A or AAAA record.

Sample Scenario

This scenario explores how a CNAME record that points to the zone apex is handled by our DNS service. In this example, a zone called example.com contains the following CNAME and A records:

CNAME record configuration:

Setting	Value
Name	@
TTL	3600
Value	www.example.com.

A record configuration:

Setting	Description
Name	www
TTL	3600
Value	192.0.2.100

Requests that point to example.com will be resolved by our authoritative DNS servers to 192.0.2.100. The requester will be unaware that example.com actually points to www.example.com.

Reverse DNS Lookup (PTR Records)

A reverse DNS lookup identifies the hostname associated with an IPv4 address by leveraging a pointer (PTR) record.

Configuration

Set up a reverse DNS lookup by performing the following steps:

1. Create a zone within the in-addr.arpa domain that is specific to the first three octets of the desired IPv4 address. Reverse the order of the first three octets when setting up your zone.

   Syntax:

   3rd Octet.2nd Octet.1st Octet.in-addr.arpa

   Example:

   Create the following zone for 192.0.2.100:

   2.0.192.in-addr.arpa

2. Create a PTR record for the desired IP address within the above zone.

   Setting	Value	Description
   Name	Fourth Octet	Set to the fourth octet of the desired IPv4 address.
   TTL	Seconds	Set the TTL to the length of time (in seconds) that a DNS server should cache the record.
   Value	Hostname.	Indicate the hostname associated with this IPv4 address.

   Example:

   Create a PTR record for 192.0.2.100 by setting the name to 100, TTL to 3600, and the value to the desired hostname (e.g., www.example.com.).

Upon setting up the above configuration, a reverse DNS lookup for 192.0.2.100 returns:

More Information

• Record administration
• Switching DNS service providers (domain delegation)

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