NAPTR

NAPTR Record

Active

The NAPTR (Naming Authority Pointer) record is used to map telephone numbers, SIP URIs, and other identifiers to services using regular expression substitution rules.

name TTL IN NAPTR order preference flags service regexp replacement

In one line

The NAPTR (Naming Authority Pointer) record is used to map telephone numbers, SIP URIs, and other identifiers to services using regular expression substitution rules. It is the backbone of ENUM (E.164 NUmber Mapping), which translates phone numbers into internet URIs. NAPTR records are processed in order using priority and weight fields.

Description

NAPTR records contain a set of rules that rewrite a domain name or URI using regular expressions, then delegate to SRV or URI lookups. They are used in VoIP systems to route SIP calls, in ENUM to convert +1-202-555-0100 into sip:[email protected], and in URI resolution schemes. Processing order is controlled by the Order field (lower = first), with Weight breaking ties.

Examples

ENUM phone mapping

shell

0.0.1.0.5.5.5.2.0.2.1.e164.arpa. IN NAPTR 100 10 "u" "E2U+sip" "!^.*$!sip:[email protected]!" .

SIP URI mapping

shell

example.com. 3600 IN NAPTR 20 50 "s" "SIP+D2U" "" _sip._udp.example.com.

Lookup NAPTR

shell

dig example.com NAPTR

Related Record Types

SRV

Specification

RFC 3403 – DNS NAPTR record specification →