Primary/Secondary ENUM Zones

Primary ENUM Zone

Primary ENUM zones serve as the authoritative source of information for mapping telephone numbers to their corresponding digital services. While in the Master DNS zone, your hostname is pointed to an IP address, the ENUM zone translates telephone numbers into Internet addresses. 

These zones play a crucial role in ensuring the accuracy and reliability of ENUM data. Therefore, the administrator of the Primary ENUM zone has full responsibility for managing and updating the mapping information.

How to add it?

You can add your Primary ENUM zone in several easy steps:

1. Login to your account.
2. Click on the "create zone" button in the DNS Hosting section.
3. Choose a type of zone (Primary/Secondary ENUM zone).
4. Enter the Telephone Number in reverse format and fill it.
5. Click on the "CREATE" button. 

The telephone number must be entered in a reverse format with dots separating each digit. For example, if you would like to add a Primary ENUM DNS zone for telephone number +11234567899, the Primary ENUM DNS zone must be: 9.9.8.7.6.5.4.3.2.1.1.e164.arpa.

Video tutorial

Secondary ENUM Zone

The Secondary ENUM DNS zone is the read-only copy of the DNS records. This means that the DNS records cannot be added directly to the Secondary ENUM DNS zone. The Secondary ENUM DNS zone can receive the updated records only from the Primary ENUM zone of the DNS server.

Secondary ENUM zones complement Primary ENUM zones by providing redundancy and improving the resilience of ENUM infrastructure. They serve as a backup, and if primary server failures, secondary ENUM zones ensure that essential ENUM data remains accessible.

How to add it?

To create a Secondary ENUM Zone, you need to:

1. Login to your account.
2. Click on the "create zone" button in the DNS Hosting section.
3. Choose a type of zone (Primary/Secondary ENUM zone).
4. Enter the Telephone Number in reverse format and fill it.
5. Enter the Master server IP.
6. Click on the "CREATE" button. 

Note that the records can be managed only from the Primary servers.

Video tutorial

ENUM NAPTR Records

NAPTR (Naming Authority Pointer) records are the backbone of ENUM Zones, enabling the mapping of telephone numbers to Internet services. Each record defines how a specific number can be translated into a URI, like a SIP or email address. NAPTR records ensure that telephone numbers are reliably resolved into digital endpoints, forming the foundation of ENUM’s functionality.

The structure of NAPTR Records in ENUM Zones is as follows:

• Order: Determines the priority of the rule; lower numbers are evaluated first.
• Preference: Resolves ties when multiple NAPTR records have the same order.
• Flags: Indicates the action, such as "u" for URI replacement.
• Service: Specifies the protocol (e.g., E2U+sip for SIP).
• Regex: A pattern that defines how the number is transformed into the desired format.
• Replacement: Points to the next domain if no direct resolution exists.

An example of NAPTR record for the telephone number +11234567899 is as follow: 

$ORIGIN 9.9.8.7.6.5.4.3.2.1.1.e164.arpa.

IN NAPTR 100 10 "u" "E2U+sip" "!^.*$!sip:info@example.com!" 

FAQ

Question: How frequently should records be updated in Primary ENUM Zones?

Answer: Records in Primary ENUM Zones should be updated regularly to ensure they reflect the current state of telephone number assignments.

Question: How often do Secondary ENUM Zones synchronize with the Primary ENUM Zone?

Answer: Secondary ENUM Zones periodically synchronize with the Primary ENUM Zone to ensure they contain the most up-to-date ENUM data. The zone administrators typically set the synchronization frequency. 

Question: What happens if the Primary ENUM Zone becomes unavailable?

Answer: If the Primary ENUM Zone becomes unavailable, the Secondary ENUM Zone acts as a backup. DNS resolvers query the Secondary ENUM Zones to retrieve ENUM mappings, ensuring continued service availability.