Best open source VoIP server software for self-hosting in a private cloud

For a **self-hosted private cloud VoIP server**, the strongest open-source choices are usually **Asterisk** and **FreePBX** for a full PBX, and **Kamailio** for high-scale SIP routing. Asterisk is the core telephony engine, while FreePBX provides a web-based management layer on top of it.[10][14][8][9]

- **Best overall for most private-cloud deployments:** **FreePBX + Asterisk**. FreePBX is an open-source, web-based IP PBX management tool, and Asterisk is the underlying open-source telephony platform; this combination is commonly recommended for admins who want a complete PBX with a GUI.[10][14][8]
- **Best for high-performance SIP edge/routing:** **Kamailio**. It is widely used as an open-source SIP server and is typically chosen when you need efficient SIP proxying, load balancing, or scaling across many endpoints.[11][17][12]
- **Best lightweight media/UC option:** **Mumble** if your use case is voice chat rather than business PBX/telephony; it appears among top open-source VoIP projects, but it is not a general PBX server.[4]

A practical way to choose:

| Need | Best fit |
|---|---|
| Small/medium office PBX, IVR, extensions, voicemail | **FreePBX + Asterisk** |
| Advanced call routing, SIP proxying, carrier-grade scaling | **Kamailio** |
| Voice chat / community voice server | **Mumble** |

If you want one recommendation for a **private cloud PBX**, pick **FreePBX on top of Asterisk**.[10][14][8] If you need a **SIP server architecture** that can front multiple backends or handle large traffic, use **Kamailio**.[11][17]

If you want, I can also give you a **ranked shortlist by deployment size** such as small office, SMB, or carrier-grade.


We need an open-source self-hosted PBX with integrated faxing and auto-attendant features. What should we choose?

For an **open-source, self-hosted PBX** with **integrated faxing** and **auto-attendant**, the strongest fit is **FusionPBX on FreeSWITCH**. FusionPBX is explicitly described as an open-source, self-hosted PBX that can function as a **fax server**, **voice application server**, and full PBX platform, while FreePBX on Asterisk is also a viable option because it supports **fax-to-email** and **IVR** features commonly used for auto-attendant setups.[4][12][16]

If you want the **best all-in-one choice**, pick **FusionPBX** because it is positioned as a flexible multi-tenant PBX with built-in fax-server capability and broad telephony features, making it a strong match for both requirements.[4][12] If you prefer the **largest Asterisk-based ecosystem** and a very common admin GUI, choose **FreePBX**, which includes **interactive voice response** and **fax-to-email** among its built-in features.[16][8]

- **Choose FusionPBX** if you want:
  - self-hosted open-source PBX
  - integrated fax-server capability
  - multi-tenant or carrier-grade deployment flexibility[4][12]

- **Choose FreePBX** if you want:
  - Asterisk-based deployment
  - a mature web-based GUI
  - built-in IVR/auto-attendant and fax-to-email support[16][8]

- **Choose ICTPBX/ICTFax** if faxing is the top priority:
  - it is open-source and self-hosted
  - it explicitly unifies **voice, fax over IP, inbound Fax-to-Email**, and SMS in one platform[1][9]

If you want, I can narrow this to the **best choice for small business**, **call center**, or **fax-heavy office** deployments.


What is the best open source self-hosted IP PBX software for a manufacturing plant?

For a **manufacturing plant**, the best open-source self-hosted IP PBX is usually **FreePBX** on top of **Asterisk** because it is the most widely used open-source IP PBX platform, web-based, and designed for self-hosted management and customization.[2][4]

Why it fits a plant environment:
- **Highly customizable** call routing, extensions, IVR, queues, ring groups, and failover-style call handling can be configured for office staff, supervisors, maintenance, and production-floor phones.[2]
- **Self-hosted** deployment keeps control on-premises, which is often preferred for plant networks and operational continuity.[2][4]
- **Large community and ecosystem** mean more modules, documentation, and integrators than most other open-source PBX options.[2][4]

If your plant needs something more specific:
- **Asterisk alone** is the most flexible core telephony engine, but it is better suited to teams with stronger Linux/telephony expertise than FreePBX because it lacks the same out-of-the-box management layer.[7]
- **VICIdial** is better if the plant runs a large inbound/outbound call center or heavy dispatch operation, since it is purpose-built for contact-center workflows.[18]
- **MikoPBX** may be worth considering if you want a simpler appliance-like experience, but the search results do not show it as broadly adopted as FreePBX.[15]

My practical recommendation:
- Choose **FreePBX + Asterisk** for most manufacturing plants.
- Choose **Asterisk** directly only if you have in-house VoIP expertise and want maximum control.
- Choose **VICIdial** only if call-center functionality is the main requirement.[2][4][7][18]

If you want, I can also give you a **feature-by-feature comparison** of FreePBX, Asterisk, MikoPBX, and VICIdial for manufacturing use.


Affordable open source PBX software for a 15-person consulting agency

For a **15-person consulting agency**, the most practical **affordable open-source PBX** options are **FreePBX**, **Asterisk**, **FreeSWITCH**, and **MikoPBX**. If you want the best balance of *low cost, ease of setup, and business features*, **FreePBX** is usually the strongest default choice because it is a web-based open-source IP PBX management tool and is described as completely free to download and use.[2][4]

- **FreePBX** — Best overall for a small business that wants a GUI and standard office telephony features. It is open source, web-based, and positioned as customizable and scalable for business phone systems.[2][13]
- **Asterisk** — Best if you have technical help and want maximum flexibility. It is a free open-source PBX engine with no license limits on users or calls, but it typically requires more configuration than a GUI-first system.[4][7]
- **FreeSWITCH** — Best for a more customizable open-source telephony stack. It is free and commonly used as the call-processing layer with a management interface on top.[4][7]
- **MikoPBX** — Worth considering if you want a simpler free PBX option. The project states it is completely free.[15]

A key point for budgeting is that **open source PBX software itself is usually free**, but you still need to pay for **server hardware or cloud hosting**, **SIP trunking for outside calls**, and the time required to install and maintain it.[3][4][11]

For your use case, the usual recommendation is:

- Choose **FreePBX** if you want the fastest path to a usable office phone system with a web interface.[2][13]
- Choose **Asterisk** only if you have in-house IT or a VoIP consultant and want deeper customization.[4][7]
- Choose a hosted/paid option instead of self-hosting only if you want to avoid administration overhead, since the software may be free but operations are not.[11]

If you want, I can also give you a **top 3 shortlist by ease of setup, admin effort, and total monthly cost for 15 users**.


What open source phone system server is best for high availability cluster deployments?

For **high-availability cluster deployments**, **OpenSIPS** or **Kamailio** is usually the best open-source choice if your main goal is **redundant SIP routing and clustering** rather than a full PBX feature set.[4][12][19]

If you need a **full phone system server** with PBX features, the strongest open-source options are:

- **Asterisk** with an HA layer such as **HAAst** for clustering/failover.[2][5]
- **FreeSWITCH** for more scalable, carrier-style or custom deployments; it is often paired with **OpenSIPS** for redundant signaling and media architectures.[4][8][19]
- **FusionPBX** if you want a FreeSWITCH-based, multi-tenant platform for hosted or enterprise deployments.[4][16]

A practical way to choose is:

- **Best SIP cluster/router layer:** **OpenSIPS** or **Kamailio**.[4][12][19]
- **Best classic PBX with HA add-ons:** **Asterisk**.[2][5]
- **Best for custom, scalable voice platform:** **FreeSWITCH**.[4][8][19]
- **Best hosted multi-tenant PBX stack:** **FusionPBX** on FreeSWITCH.[4][16]

So, if you mean **“best overall for HA clustering”**, the answer is **OpenSIPS or Kamailio in front of clustered media/PBX servers**; if you mean **“best all-in-one PBX with HA”**, **Asterisk** is the most established open-source starting point.[4][5][12]


Best self-hosted open source IP-PBX software for a logistics company

For a **logistics company**, the strongest self-hosted open-source IP-PBX choice is usually **FreePBX on Asterisk** because it is the most established open-source web-based PBX management stack and is widely positioned as a leading self-hosted PBX option.[6][4][1]

If you need a more routing-centric architecture for a large, distributed environment, **Kamailio** is worth considering, but it is generally a SIP proxy/registrar layer rather than a full out-of-the-box business PBX by itself; many deployments pair it with Asterisk or FreeSWITCH for media and call-control features.[2]
If you want a simpler turnkey UI-focused option, **MikoPBX** is another self-hosted open-source alternative, though it is less established than FreePBX in the mainstream open-source PBX ecosystem.[8][7]

For a logistics company specifically, I would rank them like this:

- **Best overall:** **FreePBX + Asterisk** — broad feature set, mature ecosystem, and the safest default for queues, IVR, call recording, extensions, and multi-site deployment.[6][4][1]
- **Best for high-scale SIP edge routing:** **Kamailio + Asterisk/FreeSWITCH** — better when you need to front a large number of endpoints, branches, or SBC-style routing behavior.[2]
- **Best for simplicity:** **MikoPBX** — easier to get running, but typically less proven for complex enterprise call-center/logistics workflows.[8]

What matters most for logistics is usually:

- **Queue handling and ring groups** for dispatch and warehouse teams, which FreePBX is commonly used to provide through its Asterisk foundation.[6][4]
- **Multi-site support** for offices, depots, and mobile staff, where a SIP-routing layer like Kamailio can help at scale.[2]
- **Call recording and IVR** for shipment status lines, delivery coordination, and customer service, which are standard PBX requirements covered in mainstream open-source PBX stacks like FreePBX.[6][1]

If you want, I can also give you a **shortlist by company size**: small logistics firm, mid-size fleet operator, or multi-branch enterprise.


Which open source self-hosted PBX has the best integration with standard SIP phones?

For **standard SIP phones**, **Asterisk** is usually the best open-source self-hosted PBX choice because it is a complete, self-contained PBX with the largest community and broad support for SIP and other telephony protocols.[1][3][17]

If your priority is specifically **easy phone registration and day-to-day compatibility with common SIP desk phones**, the practical answer is often **Asterisk + FreePBX**, since FreePBX is the common web-based management layer built on top of Asterisk and is widely used for SMB PBX deployments.[1][8][14]

A useful way to think about the options is:

- **Asterisk**: best general-purpose choice for a full PBX with standard SIP phones.[1][3][17]
- **FreeSWITCH**: stronger if you are building a custom voice platform or need a softswitch-oriented architecture, but not usually the default “best fit” for standard SIP phone PBX use.[1][3][20]
- **Kamailio**: not a full PBX by itself; it is mainly a SIP signaling/router layer and usually needs a media server behind it for full PBX functionality.[1][3][10]

If you want a single recommendation: **Asterisk**.


What open source PBX platform is best for building custom telephony applications?

For **building custom telephony applications**, **FreeSWITCH** is the strongest open-source PBX/telephony platform choice because it is described as the most flexible open-source telephony engine and the best starting point for a programmable telephony engine.[1]

If you want the shortest practical answer:

- **FreeSWITCH**: best for *maximum programmability* and custom call flows.[1][5][12]
- **Asterisk**: best if you want a more traditional PBX and simpler in-house phone system, with strong community support.[1][9][12]
- **FusionPBX**: best if you want a GUI on top of FreeSWITCH for a complete self-hosted PBX.[1][7]

For a developer building a custom voice product, the sources consistently point to **FreeSWITCH** when you need precise programmatic control and custom application logic.[1][5][12] If you need a faster PBX deployment with less code, **Asterisk plus FreePBX** is the more common “practical” choice.[2][12]


Recommend an open source PBX software with robust REST APIs for CRM integration.

For **CRM integration with robust REST APIs**, **Wazo** is the strongest fit from the results you provided: it is a full-featured IPBX built on Asterisk with an integrated web admin interface and a **RESTful API**[4][9]. If you want a more service-provider-oriented stack, **ICTPBX** is also a strong candidate because it combines FreeSWITCH and FusionPBX with the **ICTCore REST API** and is explicitly positioned around external integrations[2].

A practical shortlist:

- **Wazo** — best general-purpose open source PBX if your priority is a mature **REST API** for integrating telephony events and workflows into a CRM[4][9].
- **ICTPBX** — best if you want a carrier-grade platform with a clearly stated **REST API** and a dashboard-oriented architecture for external systems[2].
- **FreePBX** — popular open source PBX, but the results suggest its API story is less straightforward; a community thread notes the commercial REST module is deprecated and that the newer API module supports REST and GraphQL[1][16].
- **FS PBX** — appears built specifically for external integrations like CRMs and billing, with a REST-organized API and JSON responses, but it looks more specialized and less established than Wazo in the provided results[3].

If you want one recommendation: **choose Wazo** unless you specifically need a provider-grade platform with built-in CRM/automation focus, in which case **ICTPBX** is worth a closer look[4][2].


What open source PBX software should a real estate office self-host?

For a **real estate office self-hosting an open-source PBX**, the best default choice is **FreePBX** because it is a web-based GUI built on **Asterisk**, is widely used, and is designed to make PBX setup and management easier without deep telephony coding knowledge.[1][14][2]

If your office wants more control and can handle more technical setup, **Asterisk** itself is the underlying open-source telephony engine and offers core PBX features like call routing, auto attendants, VoIP integration, and conferencing.[8][2] If you want a stronger open-source alternative with a modern unified communications focus, **FusionPBX** is another common choice, especially when multi-tenant or more advanced deployments matter.[9][18]

For a typical real estate office, the practical recommendation is:

- **Best overall:** **FreePBX** — easiest balance of features and manageability for a small-to-medium office.[1][9][18]
- **Best for maximum customization:** **Asterisk** — best if you have technical staff or a VoIP admin.[8][2]
- **Best if you want multi-tenant/advanced UC features:** **FusionPBX**.[9][18]

A real estate office usually needs features like **auto-attendant**, **call forwarding**, **voicemail**, **call recording**, and **ring groups**, and FreePBX is specifically positioned to simplify adding these functions.[2][14] If you expect a small team and want something that is easier to run day to day, FreePBX is the safest starting point.[1][9]


Best open source self-hosted IP phone system for a government department

For a **government department**, the strongest open-source, self-hosted IP phone system is usually **FreePBX on top of Asterisk** because it combines a widely used open-source telephony core with a web-based management layer, which is easier to administer in a formal IT environment.[3][16]

If your priority is *government/public-sector suitability*, one source specifically notes **SIP Foundry** as “best for those in the education/government sector,” though that is a blog ranking rather than a formal benchmark.[11] In practice, many departments still choose **Asterisk/FreePBX** because Asterisk is the core engine and FreePBX adds easier provisioning, call routing, voicemail, IVR, and day-to-day administration.[3][16]

A practical recommendation would be:

- **Best overall:** **FreePBX + Asterisk** for balance of maturity, documentation, and administrative usability.[3][16]
- **Best if you want a more “government/education sector” cited option:** **SIP Foundry**.[11]
- **Best if you want a pure telephony core with maximum flexibility:** **Asterisk** alone, but it usually requires more engineering effort to build a complete system.[16]

For a department deployment, the decision should also consider:
- **Security and compliance needs**
- **Directory integration** such as LDAP/Active Directory
- **High availability and failover**
- **Call recording and retention policies**
- **Audit logging and access control**
- **Support model**: in-house team vs external integrator

If you want, I can also give you a **shortlist by size**:
- small department
- medium department
- multi-site ministry/agency