# SIP Trunks Overview

Configure carrier trunks, auth, and DID routing for inbound and outbound calls. Read the SIP Trunks guide in Hello Alex documentation.

Canonical HTML: https://docs.helloalex.ai/article/sip-trunks-overview

Path: [Documentation](/) / [SIP Trunks](/sip-trunks)

## Overview

SIP trunking matters when you need direct carrier interoperability while preserving Hello Alex conversation controls.

## How it works

- Trunk connections define registration and channel capacity, enabling telephony transport between carrier and platform.
- DID routing then maps inbound numbers to pathways so call behavior remains controllable at the application layer.

## Use cases

- Carrier-based enterprise voice routing
- Hybrid number infrastructure

## Tips

- Good to know: carrier coordination on capacity and registration policies prevents intermittent call failures.

## Trunk List

Trunk inventory status helps teams catch registration issues before they affect routing.

Confirm all active trunks show healthy status before assigning production DIDs.

- Each trunk entry surfaces health and readiness, making operational checks straightforward.
- New trunks can be added as volume or region requirements expand.
- **Status:** Healthy trunks pass registration checks.
- Good to know: channel limits negotiated with carriers should be reviewed before high-volume events.
- Operational readiness checks
- Capacity expansion planning

## Trunk Configuration

Configuration quality directly influences registration stability and call throughput.

Run registration tests after each config change and record baseline health metrics.

- Domain and credential setup establishes secure carrier registration for voice transport.
- Capacity settings define concurrent channel behavior, aligning technical limits with expected call volume.
- **SIP domain:** Carrier registration endpoint.
- Good to know: credential rotation plans should be documented before production go-live.
- New trunk onboarding
- Credential rotation validation

## DID Routing

Routing rules connect telephony entry points to business logic, turning carrier traffic into guided conversations.

Map critical DIDs first and perform real-call validation on each route.

- Each DID is mapped to pathway handling, determining what callers experience when they dial that number.
- Live test calls confirm the mapping chain from carrier ingress to pathway behavior.
- **DID:** Inbound phone number on the trunk.
- Good to know: DID-level routing is useful for business-hours and department-specific intake separation.
- Department-based DID routing
- Business-hours call segmentation

## Next step

Validate trunk health, then route one DID to a test pathway before broader production mapping.

## Related documentation

- [More SIP Trunks guides](/sip-trunks)