SIP Trunk Ports & SRV Record Behavior

Introduction

This document explains how port configuration and DNS SRV resolution work when configuring a SIP trunk in RingQ.

SIP Trunk Ports

Port Field Rules

• Port is mandatory
• Valid range: 0 – 65535

Port Behavior Logic

• Case 1: Port = 0 (SRV mode) — proxy saved without port (e.g., callcentric.com)
• System performs DNS SRV lookup

Case 2: Port > 0

• Proxy saved with port (e.g., callcentric.com:5060)
• No SRV lookup

Loading Existing SIP Trunks

• If the proxy has a port → extract the port
• If no port → default to 0

New SIP Trunk

• Default port = 0 if not provided

DNS SRV Explanation

• Query example: _sip._udp.domain.com
• Returns target server, port, and priority

Fallback

• If no SRV record is found → fall back to port 5060

Best Practice

• Use Port = 0 unless the provider requires a fixed port