NAPTR Records Explained

What is a NAPTR Record?

A NAPTR (Name Authority Pointer) record is a type of DNS record that allows for regular expression-based rewriting of domain names. It's commonly used for service discovery and advanced routing in telecommunications systems, particularly in ENUM (E.164 Number Mapping) services.

domain.com. IN NAPTR order preference flags service regexp replacement

example.com. IN NAPTR 100 10 "s" "SIP+D2U" "!^.*$!sip:info@example.com!" _sip._udp.example.com.

Common Uses

• ENUM services for telephone number mapping
• VoIP and SIP service discovery
• Service endpoint resolution
• Protocol selection and routing
• Dynamic service location

Record Fields Explained

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  Order

  Specifies the order in which records should be processed (lower numbers are processed first)

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  Preference

  Used when multiple records have the same order (lower numbers are preferred)

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  Flags

  Defines how to interpret the regexp and replacement fields (e.g., "s" for SRV lookup)

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  Service

  Specifies the service type and protocol (e.g., "SIP+D2U" for SIP over UDP)

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  Regexp

  Regular expression for rewriting the domain name

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  Replacement

  The next domain name to look up when regexp is empty

Best Practices

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  Keep it simple

  Use simple, well-documented regular expressions and clear service definitions.

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  Plan your order/preference

  Carefully plan order and preference values to ensure proper failover and load distribution.

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  Test thoroughly

  Test NAPTR records with all expected service types and regular expressions.