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TELEPHONY

Talkdesk

Talkdesk’s External SIP Trunking connects Talkdesk to Synthflow over a SIP trunk. Talkdesk routes calls to a Synthflow agent, and the agent can transfer callers back to live Talkdesk agents.

Prerequisites

RequirementDetail
TalkdeskActive account with admin access, and Talkdesk CX Cloud with SIP Trunking enabled
SynthflowEnterprise plan with a configured agent (v2.0 or later)
Phone numberAt least one DID provisioned in Talkdesk, in E.164 format
NetworkFirewall allows SIP (UDP/TCP 32681 or TLS 32682) and RTP media between Talkdesk and Synthflow, using the region addresses

Talkdesk configuration

Configure the trunk and routing in Talkdesk Admin.

SIP trunk

  1. In Talkdesk Admin, go to Integrations → SIP Trunking.
  2. Select Add SIP Trunk and configure the trunk with the values below.
  3. Under Allowed IPs, add the Synthflow signaling addresses for your region, listed under region addresses.
  4. Select Save.
FieldValue
NameSynthflow AI
SIP Server / Proxysip.synthflow.ai, or the SIP address for your region
Port32681 (UDP/TCP) or 32682 (TLS)
TransportUDP/TCP or TLS
Authentication TypeIP-based (allow the Synthflow IPs) or Digest
SIP UsernameOnly for Digest. A username you set here. Enter the same value as Username on the Synthflow number.
SIP PasswordOnly for Digest. A password you set here. Enter the same value as Password on the Synthflow number.
Max Concurrent CallsBased on your Synthflow plan and expected call volume

Inbound routing

Route inbound calls to Synthflow through Talkdesk’s call routing engine.

  1. In Talkdesk Admin, go to Voice → Ring Groups or IVR, depending on your setup.
  2. Create a routing action, or edit an existing IVR menu.
  3. Add an External Transfer or SIP Transfer step:
    • Set the destination to the DID of your Synthflow number.
    • Select the Synthflow AI SIP trunk as the outbound route.
  4. Set a timeout and a fallback to a Talkdesk agent ring group. We recommend a 30-second timeout.
  5. Save and activate the routing configuration.

For skills-based routing, use Talkdesk’s routing rules engine to send specific call types (for example by language, department, or IVR selection) to different Synthflow agent numbers.

Transfers to live agents

  1. Note your Talkdesk SIP domain, or the DID of the target agent ring group.
  2. Set the Synthflow call transfer action to route to the Talkdesk ring group DID through the SIP trunk.
  3. Talkdesk receives the transfer and routes it to the next available agent in the ring group.

Synthflow configuration

Number import

Import the Talkdesk DID as a custom number. In Synthflow, select Phone Numbers → New Phone Number → Import a Custom Number, and fill in the Import Phone Number form:

FieldValue
Phone NumberThe DID provisioned in Talkdesk, in E.164 format
SIP DomainYour Talkdesk SBC gateway hostname or IP address
UsernameThe Talkdesk trunk’s SIP username, if it uses Digest
PasswordThe Talkdesk trunk’s SIP password, if it uses Digest
Outbound ProxyYour Talkdesk SBC proxy address, if required

The SIP Domain routes Synthflow calls back into Talkdesk for PSTN termination and agent transfers. Copy the credentials exactly, because incorrect values cause registration failures.

Agent assignment

  1. Create or select an agent (v2.0 or later).
  2. Assign the number to the agent under Deploy in the agent editor.
  3. Wait 1 to 2 minutes for SIP registration to complete.

Synthflow creates the SIP trunk when you assign the number to the agent.

Call flows

ScenarioFlow
Inbound to the agentCaller → PSTN → Talkdesk → IVR or ring group → SIP transfer → Synthflow agent
Agent transfers to a live agentSynthflow agent → SIP transfer → Talkdesk SBC → ring group → live agent
Outbound from Talkdesk through the agentTalkdesk IVR or campaign → SIP trunk → Synthflow agent handles the call

Verification

TestWhat to check
Inbound callCall the Talkdesk DID from an external phone. Check that it routes to the Synthflow agent, with two-way audio.
Transfer to a live agentTrigger an escalation during a Synthflow call. Check that the call lands in the right Talkdesk ring group with caller ID intact.
Outbound from TalkdeskRoute a Talkdesk IVR call to the Synthflow trunk. Check that the agent answers.

Troubleshooting

IssueFix
Registration failsCheck the SIP Domain, credentials, and firewall (UDP/TCP 32681 or TLS 32682). Check that the Synthflow IPs are in the Talkdesk Allowed IPs.
Calls do not reach SynthflowCheck that the IVR or ring group routing action points to the Synthflow DID through the right SIP trunk.
One-way or no audioOpen RTP ports in both directions. Confirm G.711 is negotiated on both sides.
Caller ID missingSet the From header to the caller’s E.164 number. Check that Talkdesk passes the ANI in the SIP INVITE.
Transfer failsCheck that the Talkdesk ring group DID is correct and the SIP trunk is active. Check the Talkdesk transfer logs.

Resources