Tech Prefix Authentication

A 4-digit identifier prepended to outbound calls to differentiate multiple SIP connections sharing the same IP address.

Dial string format

[tech_prefix][destination_number]

Example: Tech prefix 1234 + destination +18005678912 = 123418005678912

Use cases

Multiple SIP connections from the same IP address
Granular call routing and billing per connection
Traffic stream separation

Configuration

PATCH /v2/ip_connections/

{
  "inbound": {
    "sip_subdomain_receive_settings": "from_anyone"
  },
  "outbound": {
    "tech_prefix_enabled": true
  }
}

Tech prefix value is assigned by Telnyx and visible in the connection settings.

Phone system setup

The PBX or SIP client must prepend the tech prefix to all outbound calls on the trunk.

Authentication behavior

Condition	Result
Correct tech prefix included	Call authenticated
Missing or incorrect prefix	`407 Proxy Authentication Required`

Alternative authentication methods

For connections sharing an IP address:

Method	Description
Tech prefix	4-digit prepended identifier
IP authentication token	Token-based validation
P-Charge-Info header	SIP header-based routing

IP Authentication Token

Caller ID Policy

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Getting Started

Authentication

Configuration

Routing

Network Configuration

Features

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Emergency Calling

Troubleshooting

SIP Integrations Guides

API Reference

For AI Agents

Tech Prefix Authentication

Dial string format

Use cases

Configuration

Phone system setup

Authentication behavior

Alternative authentication methods

​Dial string format

​Use cases

​Configuration

​Phone system setup

​Authentication behavior

​Alternative authentication methods

Dial string format

Use cases

Configuration

Phone system setup

Authentication behavior

Alternative authentication methods