---
title: Overview
slug: dynamic-sip-trunking
description: Discover Exotel SIP Trunking, a cloud-based solution enabling seamless internet calls, Voice AI integration, and versatile routing for contact centers and outreach platforms.
docTags: 
createdAt: 2026-01-24T08:30:00.831Z
---

This document explains what Exotel SIP Trunking is, how it works, and what problems it solves.

## What is SIP Trunking?

SIP (Session Initiation Protocol) Trunking allows you to make and receive phone calls over the internet instead of traditional telephone lines (PRI / ISDN).

With Exotel SIP Trunking, your PBX, Contact Center, or SIP-enabled system connects directly to the telephone network (PSTN) using Exotel’s cloud infrastructure.

This eliminates physical telephony hardware while enabling scalable, programmable voice connectivity.

## What Exotel Provides

Exotel acts as the SIP gateway between your system and the telephone network.

- SIP signaling and media handling
- Routing to mobile, landline, and toll-free numbers
- High availability across multiple regions
- Optional routing to Voice AI using StreamKit

## High-Level Architecture

![](https://api.archbee.com/api/optimize/SK2urIgCC2ml99YyqWOSl/jhgbf_Ptd3pZ4TBTSDNwf_screenshot-2026-01-24-at-21036apm.png)

Your system communicates with Exotel using SIP.
Exotel handles connectivity to the telephone network.

## Call Directions

Exotel SIP Trunking supports the following call directions.

### Outbound (SIP → PSTN)

Your system initiates a call to a phone number.

:::BlockQuote
`Your SIP System → Exotel → PSTN → Customer Phone`
:::

Typical use cases:

- Agent outbound calling
- Dialer campaigns
- Click-to-call from applications

Outbound calls require your server’s public IP to be whitelisted.

### Inbound (PSTN → SIP)

Your system receives calls from phone numbers.

:::BlockQuote
`Customer Phone → PSTN → Exotel → Your SIP System`
:::

Typical use cases:

- Customer support numbers
- IVR and call routing
- Contact center queues

Inbound calls are routed to an IP address or FQDN configured on the trunk.

## StreamKit (Voice AI Routing)

In addition to PSTN routing, Exotel SIP Trunking can route calls to Voice AI bots using StreamKit.

:::BlockQuote
`Your SIP System → Exotel → Voice AI (WebSocket)`
:::

This is enabled using mode: flow when mapping a phone number to a trunk.

Typical use cases:

- AI-powered IVR
- Voice bots
- Speech analytics
- Agent assist

## Supported Routing Modes

| **Mode** | **Description**                                 |
| -------- | ----------------------------------------------- |
| pstn     | Routes calls to the telephone network (default) |
| flow     | Routes calls to Voice AI using StreamKit        |

The routing mode is configured per phone number.

## What You Can Build with SIP Trunking

- Enterprise contact centers
- Outbound calling platforms
- Automated voice systems
- Voice AI integrations
- Hybrid human + bot call flows

:::Heading{depth="2" indent="1"}
**What’s Next**
:::

- To make your first call, go to **Quick Start**
- To understand routing behavior, see **Call Directions & Modes**
- To configure SIP Trunking, see **Setup**