Connect Exotel SIP Trunk to ElevenAgents by ElevenLabs

19 min

This guide explains how to connect Exotel SIP trunking to ElevenAgents by ElevenLabs so you can place and receive PSTN calls in India through Exotel while your agent runs on ElevenLabs.

GitHub repo (reference): https://github.com/exotel/AgentStream-VoiceAIEcosystem

What you will set up

Integration	Direction	When to use
Outbound SIP (digest)	ElevenLabs → Exotel → PSTN	Agent places outbound calls via your Exotel DID
Inbound SIP	PSTN → Exotel DID → ElevenLabs	Callers dial your Exotel number and reach the agent

Separate the API work: Outbound SIP uses only create trunk → map DID → credentials. Inbound SIP adds destination URI on the trunk (and Flow). Trunk ACL (whitelisted-ips) applies only when your Voice AI provider gives you a static egress IP — Exotel trunk does not support CIDR range allowlisting; use one static IP per API call (mask: 32) if needed.

Architecture

Outbound SIP (digest)

ElevenLabs → SIP digest → Exotel edge IP:port → Indian PSTN → Customer

Inbound SIP

Customer → PSTN → Exotel DID → Flow (Connect) → sip:<trunk_sid> → … → sip.rtc.elevenlabs.io → ElevenLabs Agent

Destination URI on the trunk defines where Exotel sends inbound SIP toward ElevenLabs. In the Connect applet Dial whom, use sip:<trunk_sid> only — the trunk_sid string returned from Create trunk (not a full sip:user@host URI).

For FQDN-only inbound (no digest on trunk), do not add POST .../credentials unless Exotel requires it for your design.

Prerequisites

Exotel

my.in.exotel.com with SIP trunking enabled.

KYC; Exophone (DID) in E.164 (+91…).

API Key, API Token, Account SID from API credentials.

APIs: https://api.in.exotel.com (India).

ElevenLabs

Agents / Conversational AI and SIP phone import.

Published agent; API key if testing outbound via HTTP API.

Network

SIP: TCP or TLS; RTP: UDP per Exotel network doc.

Part A — ElevenLabs (dashboard)

Outbound SIP (digest)

Agents → create/publish agent.

Phone Numbers → Import a phone number from SIP trunk.

E.164 Exotel DID; Transport TCP/TLS per Exotel; SIP digest = same values you will set in Exotel POST .../credentials.

Outbound address = Exotel edge IP:port from Exotel.

Import → assign number to agent. Note agent_phone_number_id for API tests.

Inbound SIP (ACL path)

Import number; leave digest empty if using ACL on ElevenLabs.

Allowlist Exotel signaling IPs on ElevenLabs if required (Exotel network doc).

Part B — Exotel console

Numbers, KYC, App Bazaar / Flows for Connect when using inbound.

Part C — Exotel APIs

Auth: https://API_KEY:[email protected]/... Rate limit: 200 requests/minute. Templates: _exotel-trunk-api-snippets.md.

Outbound SIP — required steps only

Create trunk

Map DID to trunk

POST .../credentials — digest; must match ElevenLabs import

Optional (only if ElevenLabs gives a static egress IP): POST .../whitelisted-ips with that single IP, mask: 32. Repeat per static IP if Exotel and your provider agree. Do not assume CIDR range whitelist on trunk.

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": "eleven_labs"
  }'

Applicability: UI-driven (ElevenLabs console for agents + phone numbers) with optional API-driven outbound triggering.

Exotel edge: Exotel provides SIP edge IP address(es) and port(s) for signaling (for example TLS 443 or TCP 5070 per Exotel network and firewall). Configure <EXOTEL_EDGE_IP>:<PORT> in ElevenLabs — use the values Exotel assigns for your account.

Edge hostnames you may see (India): in.voip.exotel.com:5070 (TCP) and in.voip.exotel.com:443 (TLS). Use the exact host/IP + port + transport Exotel assigns. See _exotel-trunk-api-snippets.md for details.

ACL vs digest (important): Avoid trying to whitelist CIDR ranges. Exotel trunk ACL is intended for static /32 IPs only (mask: 32). If a provider publishes only CIDR / shared egress ranges, prefer digest and coordinate with Exotel/provider support—mixing allowlists and digest can cause auth/routing issues in multi-tenant egress setups.

Inbound SIP — destination URI on trunk

Map inbound SIP toward ElevenLabs (host/port/transport per ElevenLabs):

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.rtc.elevenlabs.io:5060;transport=tcp" }
    ]
  }'

Connect applet (inbound)

App Bazaar → Flow → Connect applet.

Dial whom: sip:<trunk_sid> — paste the trunk_sid from the create-trunk API response (prefix sip: only; not a full SIP URI).

Map the Exophone to this Flow.

Overview: Exotel Voice AI / SIP trunking.

Test calls

Lab validation (outbound)

Outbound SIP has been tested end-to-end when trunk + DID + digest + (optional) static-IP ACL align. A connected call does not guarantee the agent speaks — see below.

Outbound API

Use ElevenAgents by ElevenLabs outbound call API — confirm the current URL in ElevenLabs API docs (paths change over time).

curl -s -X POST "https://api.elevenlabs.io/v1/convai/<outbound-call-endpoint-per-current-docs>" \
  -H "xi-api-key: ${ELEVENLABS_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "YOUR_AGENT_ID",
    "agent_phone_number_id": "YOUR_PHONE_NUMBER_ID",
    "to_number": "+91XXXXXXXXXX"
  }'

Inbound

Dial your Exotel DID; agent should answer via ElevenLabs.

Call connects but agent does not speak (no bot audio)

This section applies when the call is triggered but the agent does not play audio.

Check	Action
Assignment	Imported DID assigned to the agent used in the API
IDs	agent_phone_number_id matches the imported SIP number
Agent	Published; first message / voice configured
Logs	ElevenLabs ConvAI traces for session errors
RTP	If total silence, check UDP/RTP per Exotel network doc

Troubleshooting

Symptom	Likely cause
SIP 401	Digest mismatch (Exotel /credentials vs ElevenLabs)
SIP 403 inbound	ElevenLabs ACL vs Exotel source IPs
408 / timeout	DNS/firewall to ElevenLabs FQDN
Connect does nothing	Dial whom must be sip:<trunk_sid>, not a full URI
Call triggers, no speech	See Call connects but agent does not speak (no bot audio)

Official references

Resource	URL
Exotel SIP API	https://docs.exotel.com/dynamic-sip-trunking/detailed-sip-trunking-api-reference
Exotel + ElevenLabs	https://docs.exotel.com/dynamic-sip-trunking/elevenlabs-and-exotel-sip-trunking-integration-guide-for-voice-ai
Exotel network	https://docs.exotel.com/dynamic-sip-trunking/network-and-firewall-configuration
ElevenLabs SIP	https://elevenlabs.io/docs/agents-platform/phone-numbers/sip-trunking