What is IP PBX development?
IP PBX development is the design and deployment of software-based phone systems using Asterisk or FreeSWITCH over IP networks, replacing expensive legacy hardware PBX systems.
How much does a custom IP PBX cost?
Custom IP PBX development starts from $3,000 for small hosted deployments. Enterprise on-premise systems with CRM integration, compliance recording, and HA clustering range from $15,000–$80,000 depending on scale.
Custom IP PBX
Development Services
Enterprise-grade phone systems built on Asterisk or FreeSWITCH. Hosted, on-premise, or multi-tenant — with IVR, call recording, CRM integration, and 99.99% uptime SLA.
200+
PBX Deployments
100K+
Extensions Managed
99.99%
Uptime SLA
12+
Years Experience
Built on
Asterisk 20/21
Open Source
FreeSWITCH
High Scale
FusionPBX
Multi-Tenant
FreePBX
GUI Layer
IP PBX Development Services
End-to-end IP PBX engineering — from greenfield builds to legacy migrations, from single-site deployments to global multi-tenant platforms.
Asterisk PBX Development
Full IP PBX on Asterisk 20/21 with PJSIP. Extensions, ring groups, call queues, auto-attendant IVR, voicemail-to-email, call recording, CDR, and multi-tenant provisioning.
FreeSWITCH PBX Development
High-performance softswitch PBX on FreeSWITCH. Superior concurrency for 10,000+ simultaneous calls, native WebRTC support, mod_verto, and FusionPBX multi-tenant management.
Multi-Tenant Hosted PBX
Service provider platform supporting 100s of isolated organizations on shared infrastructure. Per-tenant branding, billing, self-service portal, and DID management.
IVR & Auto-Attendant
Multi-level IVR menus with TTS, ASR speech recognition, DTMF routing, business hours logic, dynamic CRM lookups, callback scheduling, and AI voice bot integration.
Call Recording & CDR
Compliant call recording with GDPR/HIPAA modes, encrypted storage, AI transcription, keyword search, pause/resume indicators, legal hold, and tamper-proof audit logs.
CRM Integration
Click-to-call from Salesforce, HubSpot, Pipedrive, or Zoho. Auto call logging, screen-pop on inbound, presence sync with Slack/Teams, and calendar do-not-disturb automation.
Legacy PBX Migration
Zero-downtime migration from Nortel, Avaya, Cisco CallManager, or old Asterisk/chan_sip. Parallel-run strategy, dialplan audit, user import, and cutover coordination.
PBX Security Hardening
SIP fraud prevention, fail2ban, TLS/SRTP encryption, AMI/ARI credential rotation, context isolation, STIR/SHAKEN, and ongoing security audit with monthly threat reports.
Choose Your Deployment Model
We design for hosted cloud, on-premise, and hybrid architectures — each with full redundancy and your exact compliance requirements.
Hosted / Cloud PBX
- Zero upfront hardware cost
- Automatic updates & security patches
- 99.99% uptime SLA with geo-redundancy
- Scale extensions in minutes
- CelloIP manages all infrastructure
- Ideal for SMBs & remote teams
On-Premise PBX
- Complete data sovereignty & control
- Works without internet connectivity
- Deep integration with legacy systems
- One-time hardware investment
- Customise every layer of the stack
- Ideal for enterprises & regulated industries
Hybrid PBX
- Cloud primary + on-premise failover
- Best of both worlds
- Automatic failover in < 30 seconds
- Branch offices with local survivability
- Centralised management, distributed media
- Recommended for most large enterprises
Enterprise PBX Features, Standard
Every IP PBX we build includes a comprehensive feature set — not add-ons, not extras.
Call Queues & ACD
Skill-based routing, overflow, priority queuing
Conference Bridges
Multi-party calls, PIN-protected rooms, recording
SIP Trunk Integration
Any ITSP, PSTN gateway, DID number porting
REST API / ARI
Full programmatic call control via webhooks
Call Transfer & Park
Blind, attended, DTMF park, retrieve from any extension
Business Hours Logic
Time-based routing, holiday schedules, overrides
Presence & BLF
Busy-lamp field, extension status on desk phones
Hot-Desking
Login/logout extensions on any phone in the office
Voicemail to Email
MP3 attachment, transcription, MWI notification
Real-Time Wallboard
Live agent states, queue metrics, SLA timers
HIPAA / GDPR Compliance
Encrypted storage, access control, retention policy
WebRTC Softphone
Browser-based calling without any client install
Hosted vs On-Premise: At a Glance
Unsure which model fits? This comparison covers the key decision factors.
How We Deploy Your IP PBX
A structured 6-phase process refined across 200+ deployments — from architecture to go-live in 4–8 weeks.
Discovery & Architecture
We map your call flows, user count, compliance needs, and integration requirements. Deliver a detailed architecture document with platform recommendation (Asterisk vs FreeSWITCH), hardware spec, and project timeline.
Infrastructure Setup
Server provisioning (cloud or on-premise), OS hardening, firewall and QoS configuration, SIP trunk setup, TURN/STUN for WebRTC, and HA clustering with heartbeat monitoring.
Core PBX Configuration
Extensions, dial plans, ring groups, call queues, IVR menus, voicemail, call recording, CDR database, admin web portal, and self-service user panel setup and testing.
Integrations & Custom Dev
CRM screen-pop, click-to-call, API connectors, AGI/ARI business logic, billing integration, custom reporting dashboards, and any bespoke feature development.
Testing & Load Simulation
SIP load testing to 150% projected peak, failover simulation, media quality testing (MOS scores), security penetration testing, and UAT with your team.
Go-Live & Handover
Phased cutover with parallel-run fallback, admin and end-user training, runbooks, 30-day hypercare support, and optional ongoing managed service contract.
Why CelloIP for IP PBX?
We've deployed IP PBX systems for financial services, healthcare, contact centres, and telecom providers across 30+ countries. Our track record speaks for itself — not a single production outage attributed to PBX architecture in 12+ years.
VoIP-Specialist Team
No generalists — every engineer is a certified Asterisk or FreeSWITCH specialist
NDA on Day 1
Your IP, your code, your data — complete ownership from project kick-off
Fixed-Price Projects
Scope locked upfront — no billing surprises, no scope creep surprises
Post-Go-Live Support
30-day hypercare, ongoing SLA options from 9×5 to 24×7 NOC
200+
IP PBX Deployments
Asterisk & FreeSWITCH
100K+
Extensions Managed
Across all deployments
500+
Tenants on FusionPBX
Multi-tenant hosted
< 30s
Failover Time
HA cluster handover
GDPR
Compliance Ready
HIPAA, SOC2, ISO27001
12+
Years of VoIP Engineering
Since 2012
Frequently Asked Questions
Everything you need to know before starting your IP PBX project.
What is the difference between IP PBX and a traditional PBX?+
A traditional PBX is proprietary hardware using expensive circuit-switched lines. An IP PBX is software running on standard servers, routing calls over IP networks. IP PBX is 60–80% cheaper to run, far more feature-rich, accessible from anywhere, and integrates with modern business apps. Virtually all new deployments today are IP PBX.
How many extensions can your IP PBX support?+
A single Asterisk server handles 500–2,000 extensions comfortably. For FreeSWITCH, a single server can manage 5,000+ concurrent calls. For enterprise deployments exceeding 10,000 extensions, we architect distributed systems with separate signalling, media, and database clusters — scaling linearly to 100,000+ extensions. Our largest multi-tenant FusionPBX deployment manages 500+ organisations with 100,000+ total users.
Hosted or on-premise — which should I choose?+
Hosted is ideal for SMBs, remote teams, and organisations wanting zero IT overhead and predictable monthly costs. On-premise suits enterprises with strict data residency, deep legacy integration needs, or unreliable internet. For most large organisations, we recommend a hybrid — hosted primary with on-premise survivability for < 30-second failover.
How do you migrate from our existing legacy PBX?+
We handle full end-to-end migration: export users and configurations from the old system, import into new IP PBX, configure parallel-run so both systems work simultaneously, test all call flows, then coordinate a phased cutover (usually a weekend). Users typically notice no disruption. Migration from Avaya, Cisco CallManager, Nortel, or old Asterisk chan_sip systems takes 2–4 weeks.
Can the PBX integrate with our CRM?+
Yes — we have pre-built integrations with Salesforce, HubSpot, Pipedrive, Zoho, and Freshdesk. Inbound calls trigger an automatic screen-pop showing the customer record. Calls are logged automatically with duration and recording link. Outbound calling via click-to-call from within the CRM. Custom API integrations are available for any CRM with a REST or SOAP API.
What uptime SLA do you offer?+
Our hosted IP PBX achieves 99.99% uptime (< 52 minutes downtime/year) through dual data centres, active-active clustering, automated health checks with < 30-second failover, and 24×7 NOC monitoring. On-premise systems can achieve the same with proper HA design — we specify and deploy the redundancy architecture as part of every project.
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Ready to Deploy Your IP PBX?
Get a free 30-minute architecture review. We'll assess your call volume, compliance needs, and integration requirements — then recommend the exact platform and deployment model for your organisation.
NDA on Day 1 · Fixed-price engagement · Full source code ownership