Build a Modern Voice Infrastructure with Zero Complexity
If you’re running a business, building a SaaS product, or managing a call center, your SIP (Session Initiation Protocol) setup is the foundation of your entire voice communication system. But traditional PBX and open-source systems often make SIP configuration feel like a maze — manual configs, hardware dependencies, confusing extensions, and rigid limits.
Opentact simplifies all of it.
With Opentact, you can create SIP domains, add unlimited SIP users, assign numbers, build call flows, and manage everything from a clean, cloud-based dashboard — no command line, no PBX hardware, and no per-seat licensing.
This guide walks you through exactly how to set up SIP domains and users in Opentact, and how to use them to build a scalable, secure, future-proof communication system.
1️⃣ What Is a SIP Domain in Opentact?
A SIP domain is the main identity of your communication environment.
Think of it like your organization’s “voice workspace.”
Example: yourcompany.opentact.cloud
All your SIP users register through this domain, and you control how inbound and outbound calls flow across it.
A single Opentact account can have:
✔ Unlimited SIP domains
✔ Unlimited SIP users inside each domain
✔ Unlimited flexibility in routing & configuration
This is perfect for:
Multi-branch companies
Call centers
SaaS apps provisioning users
Agencies managing multiple clients
Developers building voice products
2️⃣ Create Your SIP Domain
Inside your Opentact dashboard:
Go to SIP Domains
Click Create New Domain
Choose a unique subdomain
Set security, routing, and default behaviors
Save the configuration
That’s it — your domain is now live.
Why Multiple SIP Domains Matter
You can use separate domains for:
Different departments (support.sales.opentact.cloud)
Different clients
Different brands
Staging vs production environments
Opentact gives you full multi-domain control without complexity.
3️⃣ Add SIP Users (Unlimited & Instant)
Each SIP user is an endpoint identity — perfect for:
Employees
Agents
Softphone users
AI voice bots
Internal applications
Developer test setups
To add users:
Open your SIP Domain
Click Create SIP User
Assign a username
Set a password
Apply restrictions (optional)
Save
These credentials can be used on any SIP device or softphone.
No Limits. No Licensing. No Extra Fees.
Most providers charge per user or per device. Opentact charges nothing extra — ever.
4️⃣ Connect SIP Users to Devices
Your SIP users can log in via:
IP desk phones
Softphones (Zoiper, Linphone, MicroSIP)
WebRTC (Opentact browser dialer)
Mobile VoIP apps
Custom-built SIP apps
AI-powered voice bots
All you need is:
SIP domain
Username
Password
Opentact handles registration, routing, and authentication automatically.
5️⃣ Add Phone Numbers and Routing Rules
Once your domain and users are active, you can assign numbers from Opentact’s inventory.
Route inbound calls to:
A specific SIP user
A call flow (IVR, recording, queue)
A group of users
An API response
A WebRTC endpoint
Route outbound calls with:
SIP outbound trunks
Headless API routing
Custom call flows
Least-cost routing configurations
Opentact gives you full control — without PBX complexity.
6️⃣ Secure Your SIP Environment
Opentact takes SIP security seriously with built-in protection:
TLS + SRTP for encrypted calls
IP whitelisting
Geo-blocking
Call rate limits
Fraud detection
Regulated caller ID policies
Traffic anomaly alerts
Even with unlimited SIP users, your system stays secure.
7️⃣ Monitor and Manage SIP Users at Scale
From the Opentact dashboard, you can oversee:
Real-time registration status
Active calls
Call logs
Outbound attempts
Recording activity
Per-user usage statistics
Everything is visible, searchable, and exportable — no need for external monitoring tools.
8️⃣ Automate SIP Provisioning with APIs (Developer Favorite)
For SaaS apps, CPaaS products, or large enterprises, Opentact’s APIs can automate everything:
Create new SIP domains
Provision SIP users dynamically
Fetch call logs
Add numbers
Link SIP users to devices
Pull recordings & analytics
Perfect for:
Call center platforms
Sales dialers
VoIP-enabled SaaS products
Multi-tenant applications
Opentact becomes the engine behind your communication infrastructure.
9️⃣ Build Call Flows Connected to SIP Users
With the drag-and-drop call flow builder, you can connect SIP users to:
IVR menus
Call queues
AI voice bots
Time-based routing
Failover routing
Call recording modules
Your entire communication logic lives in the cloud — configurable in minutes.
1️⃣0️⃣ Scale Without Limits or Compromises
Opentact’s SIP engine is built for growth:
✔ Add thousands of users
✔ Manage multiple domains
✔ Connect global teams
✔ Run high-volume call centers
✔ Build developer-first telephony apps
You never outgrow the platform — and you never pay per-seat fees.
Conclusion: SIP Management Doesn’t Need to Be Complicated
With Opentact, SIP domains and users become easy to manage, fast to deploy, and powerful enough to support any communication workflow — from small teams to global enterprise operations.
The combination of unlimited users, secure routing, API automation, and cloud simplicity makes Opentact one of the most versatile SIP engines on the market.
Whether you're building a modern PBX, a call center, a SaaS app, or an internal communication system, Opentact gives you the speed, flexibility, and reliability your business needs.
🚀 Start building your SIP ecosystem the smarter way. 👉 Learn more at www.opentact.org!