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On this page
  • Prerequisites
  • 8x8 Configuration
  • Create the SIP Trunk
  • Configure Inbound Routing (8x8 → Synthflow)
  • Configure Transfer Back to 8x8 (AI → Live Agent)
  • Synthflow Configuration
  • Add the SIP Number
  • Attach to the Assistant
  • Call Flow Summary
  • Verification
  • Quick Troubleshooting
  • Reference
Telephony

SIP Integration with 8x8

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SIP trunking is only available on the Synthflow Enterprise Plan.

This guide covers connecting 8x8 XCaaS (eXperience Communications as a Service) to Synthflow via SIP trunk. 8x8 routes calls to a Synthflow AI agent, which handles AI-driven conversations and transfers callers back to live 8x8 contact center agents.

Prerequisites

RequirementDetail
8x8Active XCaaS or Contact Center account with Admin access; SIP Trunking / BYOC enabled
SynthflowEnterprise Plan with a configured AI assistant (v2.0+)
Phone NumberAt least one DID provisioned in 8x8 (E.164 format)
NetworkFirewall allows SIP (UDP/TCP 32681 or TLS 32682) and RTP media between 8x8 and Synthflow

8x8 Configuration

All configuration is done in the 8x8 Admin Console (admin.8x8.com) under Telephony → SIP Trunks.

Create the SIP Trunk

  1. In 8x8 Admin Console, navigate to Telephony → SIP Trunks → External SIP Trunks.
  2. Click Add Trunk.
  3. Configure the trunk:
FieldValue
NameSynthflow AI
Primary SIP Serversip.synthflow.ai
Port32681 (UDP/TCP) or 32682 (TLS)
Transport ProtocolUDP/TCP or TLS
Authentication MethodIP-based (whitelist Synthflow IPs) or Digest
UsernameFrom Synthflow — only required if using Digest auth
PasswordFrom Synthflow — only required if using Digest auth
Max Concurrent SessionsPer your Synthflow plan / expected call volume
  1. Under IP Access Control, add Synthflow’s SIP signaling IP addresses. Contact Synthflow support for the current IP list.
  2. Click Save.

Use port 32681 for UDP/TCP and port 32682 for TLS.

Configure Inbound Routing (8x8 → Synthflow)

To route inbound calls from 8x8 to Synthflow:

  1. In 8x8 Admin Console, go to Contact Center → Queues (or IVR Menus).
  2. Edit the queue or IVR menu associated with your inbound DID.
  3. Add an External Transfer action and configure:
    • Destination: The DID associated with your Synthflow SIP number (E.164 format).
    • Trunk: Select the Synthflow AI SIP trunk.
  4. Set a timeout and configure a fallback to an 8x8 agent queue.
  5. Save the configuration.

For skills-based or schedule-based routing, use 8x8’s routing rules to conditionally route calls to Synthflow based on time of day, queue depth, or caller attributes.

Configure Transfer Back to 8x8 (AI → Live Agent)

  1. Note your 8x8 SBC hostname or IP and the DID for the target agent queue.
  2. Configure Synthflow’s transfer action to route to the 8x8 queue DID via the SIP trunk.
  3. 8x8 receives the SIP transfer and routes to the next available agent in the queue.

Synthflow Configuration

Add the SIP Number

  1. Go to the Synthflow Phone Numbers page.
  2. Click Add Number → Custom / SIP.
  3. Enter the phone number in E.164 format (same DID provisioned in 8x8).
  4. Fill in the SIP connection details:
FieldValue
Termination URIYour 8x8 SBC gateway hostname or IP address
SIP UsernameYour SIP authentication username
SIP PasswordYour SIP authentication password
Outbound Proxy (if required)8x8 SBC proxy address (if required)

The Termination URI is your 8x8 SBC address — this routes Synthflow outbound calls and transfers back into the 8x8 platform.

Be precise when copying SIP credentials. Incorrect values will cause registration failure.

Attach to the Assistant

  1. Go to Assistants and create or select an assistant (v2.0+).
  2. In the assistant settings, attach the SIP number you just created.
  3. Wait 1–2 minutes for SIP registration to complete.

The SIP trunk is created at the moment of attaching the SIP number to the assistant.

Call Flow Summary

ScenarioFlow
Inbound to AICaller → PSTN → 8x8 → Queue/IVR → External Transfer → Synthflow AI Agent
AI transfers to live agentSynthflow AI → SIP transfer → 8x8 SBC → Agent Queue → Live Agent
Outbound from 8x8 via AI8x8 IVR/campaign → SIP Trunk → Synthflow AI → handles call

Verification

TestWhat to check
Inbound callCall the 8x8 DID from an external phone. Verify it routes to Synthflow AI. Check two-way audio.
Transfer to live agentTrigger escalation during a Synthflow call. Confirm the call lands in the correct 8x8 queue with caller ID intact.
Outbound from 8x8Route an 8x8 IVR call to Synthflow. Verify the AI agent answers.

Quick Troubleshooting

IssueFix
Registration failsCheck Termination URI, credentials, and firewall (UDP/TCP 32681 or TLS 32682). Verify Synthflow IPs are in the 8x8 IP access control list.
Calls not reaching SynthflowConfirm IVR/queue external transfer points to the Synthflow DID via the correct trunk.
One-way or no audioEnsure RTP ports are open bidirectionally. Confirm G.711 codec is negotiated.
Caller ID missingSet From header to caller’s E.164 number. Verify 8x8 INVITE passes ANI correctly.
Max sessions exceededIncrease the Max Concurrent Sessions limit on the 8x8 SIP trunk or upgrade your Synthflow plan.

Reference

  • 8x8 Admin Console: admin.8x8.com
  • 8x8 SIP Trunking Documentation: docs.8x8.com (search “SIP Trunking”)
  • 8x8 XCaaS Developer Portal: developer.8x8.com
  • Synthflow SIP Overview: docs.synthflow.ai/about-sip
  • Synthflow X-EI SIP Header: docs.synthflow.ai/x-ei-sip-header