What does the 'u' flag mean in a NAPTR record?

The 'u' flag designates a terminal lookup, meaning the output of the regular expression rewrite is a final URI (such as a SIP URI) rather than another DNS domain.

Updated: August 2026 • Verified v1.2

DNS NAPTR (Naming Authority Pointer) Record Generator for ENUM & SIP

Internet & NetworkNew

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<owner> IN NAPTR <order> <pref> "<flags>" "<services>" "<regexp>" <replacement>

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Understanding Your Results

Constructs standards-compliant NAPTR zone entries (order, preference, flags, services, regexp, replacement) with presets for SIP, SIPS, and mailto routing.

Practical Guidance & Next Steps

Lower order values are evaluated first. If orders match, lower preference numbers take precedence. In ENUM, flags are typically terminal 'u' (URI lookup).

What is this?

A network telephony tool that generates RFC-compliant DNS Naming Authority Pointer (NAPTR) records for VoIP and ENUM resolution.

How does it work?

1. Enter the target domain or E.164 reverse arpa domain. 2. Configure order, preference, terminal flag, and service string (e.g. E2U+sip). 3. Input regex rewrite rules and copy the generated BIND9 zone file record.

Why use it?

Eliminates syntax and regex delimiter mistakes when configuring mission-critical VoIP and carrier routing DNS infrastructures.

Technical Scope & Calculation Limitations

Complies with RFC 2915 and RFC 3403. Regular expressions use POSIX Extended syntax delimited by exclamation marks (!).

Frequently Asked Questions

A Naming Authority Pointer (NAPTR) record is a DNS resource record used primarily by Internet telephony (VoIP/ENUM) to map telephone numbers or URNs into SIP URIs.

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