Exotel SIP Trunking – Quick Start

14 min

This guide helps you make your first outbound and inbound call using Exotel SIP Trunking.

By the end of this guide, you will:

Make outbound calls from your SIP system to PSTN

Receive inbound calls from PSTN to your SIP system

Prerequisites

Create or use Exotel account

Completed KYC

API credentials

At least one Exophone (DID)

SIP system (PBX / SBC / Contact Center) with:

Public static IP/Credentials

SIP over TLS or TCP enabled

refer Network & Firewall Configuration

You will need:

API Key

API Token

Account SID

Step 1: Create SIP Trunk

Create a logical SIP trunk.

curl -s -X POST "https://<api_key>:<api_token>@<subdomain>/v2/accounts/<account_sid>/trunks" \
  -H "Content-Type: application/json" \
  -d '{
    "trunk_name": "my_trunk",
    "nso_code": "ANY-ANY",
    "domain_name": "<account_sid>.pstn.exotel.com"
  }'

Save the trunk_sid.

Step 2: Map Phone Number to Trunk

Associate your Exophone (DID) with the trunk.

curl -s -X POST "https://<api_key>:<api_token>@<subdomain>/v2/accounts/<account_sid>/trunks/<trunk_sid>/phone-numbers" \
  -H "Content-Type: application/json" \
  -d '{
    "phone_number": "+919876543210"
  }'

Default mode is pstn

Save the numeric id from the response

Step 3(a): Map ACL for Outbound SIP(Whitelist IPs)

This is required for Outbound/Termination SIP - allowing your system to send calls through the trunk.

Use only when your Voice AI provider gives a single static egress IP that you must allow. Repeat the call for each distinct static IP (no CIDR ranges on trunk, or you have a dedicated call server).

Required for:

Outbound calls

SIP authentication

IP-based inbound destinations

curl -s -X POST "https://<api_key>:<api_token>@<subdomain>/v2/accounts/<account_sid>/trunks/<trunk_sid>/whitelisted-ips" \
  -H "Content-Type: application/json" \
  -d '{
    "ip": "<your_public_ip>",
    "mask": 32
  }'

Step 3(b): Create SIP digest credentials (outbound auth)

POST /v2/accounts/{ACCOUNT_SID}/trunks/{TRUNK_SID}/credentials

Use the same user_name and password on the Voice AI platform (ElevenLabs SIP digest, LiveKit authUsername / authPassword, Retell termination, etc.).

curl -s -X POST \
  "https://${API_KEY}:${API_TOKEN}@${SUBDOMAIN}/v2/accounts/${ACCOUNT_SID}/trunks/${TRUNK_SID}/credentials" \
  -H "Content-Type: application/json" \
  -d '{
    "user_name": "SIP_USER",
    "password": "SIP_PASS",
    "friendly_name": "voice_ai_platform"
  }'

Step 4: Map Destination URI for Inbound SIP (Mandatory)

Configures where incoming calls should be routed. This is required for Inbound/Origination calls - routing calls from the telephone network to your system.

This defines the network endpoint of the trunk.

Using IP

(IP must be whitelisted in Step 3)

curl -s -X POST "https://<api_key>:<api_token>@<subdomain>/v2/accounts/<account_sid>/trunks/<trunk_sid>/destination-uris" \
-H "Content-Type: application/json" \
  -d '{
    "destinations": [
      {
        "destination": "<your_public_ip>:5061;transport=<tls/tcp>"
      }
    ]
  }'

Using FQDN

(No IP whitelist required)

curl -s -X POST "https://<api_key>:<api_token>@<subdomain>/v2/accounts/<account_sid>/trunks/<trunk_sid>/destination-uris" \
  -H "Content-Type: application/json" \
  -d '{
    "destinations": [
      {
        "destination": "sip.yourcompany.com:5061;transport=<tls/tcp>"
      }
    ]
  }'

Step 5: Create Flow for Inbound Calls

Inbound calls are routed through Exotel Flow.

Go to App Bazaar https://my.in.exotel.com/apps

Create a new Flow

Add Connect Applet

In Dial Whom, enter:

sip:<trunk_sid>

This connects the Flow to your SIP Trunk.

Step 6: Map DID to Flow

Bind the Exophone (DID) to the Flow.

Go to Exophone Manager https://my.in.exotel.com/numbers

Select your number or purchase

Set Exopone to the Flow created above

Inbound call path is now:

PSTN → Exotel → DID→ Flow(Connect Applet)→ SIP Trunk → Destination URI → Your SIP system

Step 7: Configure SIP System

Setting	Value
SIP Domain	<account_sid>.pstn.exotel.com
Port	443 (TLS) or 5070 (TCP)
Transport	TCP or TLS
Authentication	IP-based

Ensure RTP ports (UDP 10000–40000) are open.

Step 8: Test Calls

Outbound

Dial any PSTN number from your SIP system

Inbound

Call your Exophone from a mobile phone

If both succeed, setup is complete.

Flow Mode Clarification (Important)

Flow Type	Phone Number Mode
Connect Applet (sip:<trunk_sid>)	pstn
Voicebot / other App Bazaar applets	flow

Destination URI is required in all cases.