3CX BASIC CERTIFICATION EXAM PREP
2026/2027 Update | 100+ Questions and Verified Answers | 100% Correct
Aligned with the 3CX Basic Certification Curriculum and 3CX v20 Examination Standards
VERIFIED ANSWERS +
120 QUESTIONS 7 SECTIONS 3CX V20 ALIGNED
RATIONALES
CANDIDATE INSTRUCTIONS
This examination preparation document contains exactly 120 multiple-choice questions aligned with the 3CX Basic
Certification examination domains, organized into seven content sections spanning system fundamentals and installation,
networking and firewall configuration, SIP trunking and VoIP fundamentals, extension management and call routing, security
and maintenance, remote connectivity with SBC, and advanced scenario-based challenges. Each question offers four options
(A-D) with ONE best answer; select the single most appropriate administrative action or interpretation based on current 3CX
v20 system administration practice. Questions reflect a mix of approximately 30% recall, 50% application, and 20% analysis
items, with roughly 75% presented as real-world scenario tasks involving port configuration, codec selection, SIP trunk
troubleshooting, firewall checks, licensing decisions, and remote provisioning. A verified answer and a comprehensive
rationale follow every item, explaining why the correct choice is right and why each distractor represents a common 3CX
administration pitfall. Suggested time: 120 minutes, closed reference.
SECTION 1 - SYSTEM FUNDAMENTALS, INSTALLATION & REQUIREMENTS
OS Requirements • FQDN • Deployment Models • License Types • Virtualization | Questions 1-25
Q1: A VoIP consultant is preparing a brand-new on-premise installation of 3CX v20 for a 40-user
company. Which operating system is the primary supported platform for this deployment?
A. Windows Server 2012 R2 64-bit
B. Debian 11 (64-bit) [CORRECT]
C. Ubuntu Server 22.04 LTS
D. CentOS Stream 9
Correct Answer: B
Rationale: Debian 11 64-bit is the primary supported platform for 3CX v20 installations, and the official 3CX ISO, install
script, and preconfigured VM images are all built on it. Windows Server 2019 and newer remain a supported alternative, but
Windows Server 2012 R2 is no longer an acceptable host. Ubuntu and CentOS, regardless of version, are not on the 3CX
supported platform list and will not receive validated builds. All supported platforms are 64-bit only.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 1 of 44
,3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q2: Before installing 3CX v20, the administrator must satisfy the mandatory addressing prerequisite.
Which statement correctly describes the FQDN requirement?
A. A static public IP address alone is sufficient; no domain name is needed.
B. Any internal hostname ending in .local will resolve correctly once the PBX is online.
C. The PBX must be reachable through a fully qualified domain name that resolves in public
DNS, either a 3CX-hosted subdomain or a custom domain. [CORRECT]
D. The FQDN only matters for web access and can be skipped when phones are provisioned
manually.
Correct Answer: C
Rationale: A publicly resolvable FQDN is a mandatory prerequisite: provisioning, the 3CX Apps, remote clients, and
certificate issuance all depend on it. The name can be a free 3CX-managed subdomain such as mypbx.3cx.com or the
company's own custom domain, and it must resolve in public DNS. A bare IP address or a .local hostname cannot support
certificates or remote provisioning. The FQDN is equally required for phone provisioning, so option D is a common but fatal
misconception.
Q3: A reseller is selecting a hypervisor for a customer's new 3CX v20 virtual machine. Which platform
is NOT on 3CX's officially supported virtualization list?
A. Microsoft Hyper-V
B. VMware ESXi
C. Linux KVM
D. Oracle VirtualBox [CORRECT]
Correct Answer: D
Rationale: 3CX officially supports deployment on Hyper-V, VMware ESXi, KVM, and XenServer, and publishes
preconfigured VM images for the mainstream hypervisors. Oracle VirtualBox is a desktop-class hypervisor that is not
supported for production 3CX installations. Running on an unsupported hypervisor means performance problems and
configuration issues will not be covered by 3CX support. The supported list exists because virtualization behavior directly
affects audio quality and timing.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 2 of 44
,3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q4: An administrator plans to install 3CX on an existing Windows server that already runs the
company's DNS and directory services. What is the correct recommendation?
A. Do not co-install; 3CX must not share a server with services such as DNS, Exchange, MS SQL,
or VPN because of port conflicts, resource contention, and security exposure. [CORRECT]
B. Install 3CX alongside them and simply change the 3CX web port to 80.
C. Co-installation is fully supported as long as the server has 8 GB of RAM.
D. Co-installation is recommended because it reduces the number of servers to license.
Correct Answer: A
Rationale: 3CX must have exclusive use of its ports (5060, 5090, 5001, and the RTP range), and services such as DNS,
DHCP, Exchange, MS SQL, and VPN either conflict on ports or compete for CPU and disk, degrading audio quality. A PBX is
also an internet-facing service, so co-hosting widens the attack surface of the directory infrastructure. Option B is wrong
because port 80 is not a supported replacement strategy, and RAM capacity alone does not remove conflicts. The correct design
is a dedicated PBX host or dedicated VM.
Q5: A business expects up to 32 simultaneous calls at peak. What is the MINIMUM 3CX edition that
supports this requirement?
A. Standard (16 SC)
B. Pro (64 SC) [CORRECT]
C. Free
D. Standard with an SC expansion pack
Correct Answer: B
Rationale: Simultaneous call (SC) capacity is licensed per edition: the Free edition allows 2 SC, Standard allows 16 SC, and
Pro allows 64 SC. Since 32 concurrent calls exceeds the Standard ceiling of 16, the minimum suitable edition is Pro with its 64
SC capacity. There is no SC expansion pack that raises Standard beyond its limit, making option D a common trap. Enterprise
would also work but is not the minimum.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 3 of 44
, 3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q6: Which set of prerequisites must ALL be satisfied before a 3CX PBX can be installed, activated,
and operated?
A. A VPN tunnel to 3CX headquarters, a dedicated GPU, and a static MAC address.
B. An on-premise Exchange server, a public IPv6 prefix, and a hardware SIP proxy.
C. A valid FQDN, a properly configured firewall with the required forwarded ports, and
unrestricted internet access. [CORRECT]
D. A Microsoft .NET 3.5 runtime, a DHCP reservation, and an internal-only DNS record.
Correct Answer: C
Rationale: 3CX requires a valid FQDN that resolves publicly, a firewall correctly configured with the required ports
forwarded, and continuous internet access, because the system cannot be installed, activated, or operated without internet
connectivity. Exchange servers and hardware SIP proxies are explicitly unwanted on the PBX host, and .NET 3.5 is the wrong
framework version even for Windows deployments. An internal-only DNS record defeats remote provisioning and certificate
issuance. Option C is the only set that matches the documented installation prerequisites.
Q7: What technology underpins the 3CX Web Client, and what must users install to run it?
A. It is a pure HTML5/JavaScript application, so users need only a supported browser - no plugins
or add-ons. [CORRECT]
B. It is a Silverlight application requiring a browser plugin on first use.
C. It is a Java applet that downloads a local client at each login.
D. It is a native Windows application installed through the Microsoft Store.
Correct Answer: A
Rationale: The 3CX Web Client is built natively on HTML5 and JavaScript, so any modern supported browser (Chrome,
Edge, Firefox) can run it without plugins, add-ons, or downloads. Legacy plugin-based architectures such as Silverlight or Java
applets are precisely what 3CX moved away from in v20. This design is also what enables WebRTC-based calling directly from
the browser. Describing it as a Store-installed native application confuses the Web Client with the 3CX desktop App.
Q8: Which browser is NOT supported for use with the 3CX Web Client?
A. Google Chrome
B. Microsoft Edge
C. Mozilla Firefox
D. Internet Explorer 11 [CORRECT]
Correct Answer: D
Rationale: 3CX supports the modern evergreen browsers Chrome, Edge, and Firefox for the Web Client. Internet Explorer 11
is a legacy browser without the WebRTC and modern JavaScript support the client requires, so it is not supported. Attempting
to use IE11 typically produces broken login pages and no audio path for WebRTC calls. Chrome, Edge, and Firefox are all
validated on both desktop operating systems 3CX supports.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 4 of 44
2026/2027 Update | 100+ Questions and Verified Answers | 100% Correct
Aligned with the 3CX Basic Certification Curriculum and 3CX v20 Examination Standards
VERIFIED ANSWERS +
120 QUESTIONS 7 SECTIONS 3CX V20 ALIGNED
RATIONALES
CANDIDATE INSTRUCTIONS
This examination preparation document contains exactly 120 multiple-choice questions aligned with the 3CX Basic
Certification examination domains, organized into seven content sections spanning system fundamentals and installation,
networking and firewall configuration, SIP trunking and VoIP fundamentals, extension management and call routing, security
and maintenance, remote connectivity with SBC, and advanced scenario-based challenges. Each question offers four options
(A-D) with ONE best answer; select the single most appropriate administrative action or interpretation based on current 3CX
v20 system administration practice. Questions reflect a mix of approximately 30% recall, 50% application, and 20% analysis
items, with roughly 75% presented as real-world scenario tasks involving port configuration, codec selection, SIP trunk
troubleshooting, firewall checks, licensing decisions, and remote provisioning. A verified answer and a comprehensive
rationale follow every item, explaining why the correct choice is right and why each distractor represents a common 3CX
administration pitfall. Suggested time: 120 minutes, closed reference.
SECTION 1 - SYSTEM FUNDAMENTALS, INSTALLATION & REQUIREMENTS
OS Requirements • FQDN • Deployment Models • License Types • Virtualization | Questions 1-25
Q1: A VoIP consultant is preparing a brand-new on-premise installation of 3CX v20 for a 40-user
company. Which operating system is the primary supported platform for this deployment?
A. Windows Server 2012 R2 64-bit
B. Debian 11 (64-bit) [CORRECT]
C. Ubuntu Server 22.04 LTS
D. CentOS Stream 9
Correct Answer: B
Rationale: Debian 11 64-bit is the primary supported platform for 3CX v20 installations, and the official 3CX ISO, install
script, and preconfigured VM images are all built on it. Windows Server 2019 and newer remain a supported alternative, but
Windows Server 2012 R2 is no longer an acceptable host. Ubuntu and CentOS, regardless of version, are not on the 3CX
supported platform list and will not receive validated builds. All supported platforms are 64-bit only.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 1 of 44
,3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q2: Before installing 3CX v20, the administrator must satisfy the mandatory addressing prerequisite.
Which statement correctly describes the FQDN requirement?
A. A static public IP address alone is sufficient; no domain name is needed.
B. Any internal hostname ending in .local will resolve correctly once the PBX is online.
C. The PBX must be reachable through a fully qualified domain name that resolves in public
DNS, either a 3CX-hosted subdomain or a custom domain. [CORRECT]
D. The FQDN only matters for web access and can be skipped when phones are provisioned
manually.
Correct Answer: C
Rationale: A publicly resolvable FQDN is a mandatory prerequisite: provisioning, the 3CX Apps, remote clients, and
certificate issuance all depend on it. The name can be a free 3CX-managed subdomain such as mypbx.3cx.com or the
company's own custom domain, and it must resolve in public DNS. A bare IP address or a .local hostname cannot support
certificates or remote provisioning. The FQDN is equally required for phone provisioning, so option D is a common but fatal
misconception.
Q3: A reseller is selecting a hypervisor for a customer's new 3CX v20 virtual machine. Which platform
is NOT on 3CX's officially supported virtualization list?
A. Microsoft Hyper-V
B. VMware ESXi
C. Linux KVM
D. Oracle VirtualBox [CORRECT]
Correct Answer: D
Rationale: 3CX officially supports deployment on Hyper-V, VMware ESXi, KVM, and XenServer, and publishes
preconfigured VM images for the mainstream hypervisors. Oracle VirtualBox is a desktop-class hypervisor that is not
supported for production 3CX installations. Running on an unsupported hypervisor means performance problems and
configuration issues will not be covered by 3CX support. The supported list exists because virtualization behavior directly
affects audio quality and timing.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 2 of 44
,3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q4: An administrator plans to install 3CX on an existing Windows server that already runs the
company's DNS and directory services. What is the correct recommendation?
A. Do not co-install; 3CX must not share a server with services such as DNS, Exchange, MS SQL,
or VPN because of port conflicts, resource contention, and security exposure. [CORRECT]
B. Install 3CX alongside them and simply change the 3CX web port to 80.
C. Co-installation is fully supported as long as the server has 8 GB of RAM.
D. Co-installation is recommended because it reduces the number of servers to license.
Correct Answer: A
Rationale: 3CX must have exclusive use of its ports (5060, 5090, 5001, and the RTP range), and services such as DNS,
DHCP, Exchange, MS SQL, and VPN either conflict on ports or compete for CPU and disk, degrading audio quality. A PBX is
also an internet-facing service, so co-hosting widens the attack surface of the directory infrastructure. Option B is wrong
because port 80 is not a supported replacement strategy, and RAM capacity alone does not remove conflicts. The correct design
is a dedicated PBX host or dedicated VM.
Q5: A business expects up to 32 simultaneous calls at peak. What is the MINIMUM 3CX edition that
supports this requirement?
A. Standard (16 SC)
B. Pro (64 SC) [CORRECT]
C. Free
D. Standard with an SC expansion pack
Correct Answer: B
Rationale: Simultaneous call (SC) capacity is licensed per edition: the Free edition allows 2 SC, Standard allows 16 SC, and
Pro allows 64 SC. Since 32 concurrent calls exceeds the Standard ceiling of 16, the minimum suitable edition is Pro with its 64
SC capacity. There is no SC expansion pack that raises Standard beyond its limit, making option D a common trap. Enterprise
would also work but is not the minimum.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 3 of 44
, 3CX BASIC CERTIFICATION - EXAMINATION PREPARATION 2026/2027
Q6: Which set of prerequisites must ALL be satisfied before a 3CX PBX can be installed, activated,
and operated?
A. A VPN tunnel to 3CX headquarters, a dedicated GPU, and a static MAC address.
B. An on-premise Exchange server, a public IPv6 prefix, and a hardware SIP proxy.
C. A valid FQDN, a properly configured firewall with the required forwarded ports, and
unrestricted internet access. [CORRECT]
D. A Microsoft .NET 3.5 runtime, a DHCP reservation, and an internal-only DNS record.
Correct Answer: C
Rationale: 3CX requires a valid FQDN that resolves publicly, a firewall correctly configured with the required ports
forwarded, and continuous internet access, because the system cannot be installed, activated, or operated without internet
connectivity. Exchange servers and hardware SIP proxies are explicitly unwanted on the PBX host, and .NET 3.5 is the wrong
framework version even for Windows deployments. An internal-only DNS record defeats remote provisioning and certificate
issuance. Option C is the only set that matches the documented installation prerequisites.
Q7: What technology underpins the 3CX Web Client, and what must users install to run it?
A. It is a pure HTML5/JavaScript application, so users need only a supported browser - no plugins
or add-ons. [CORRECT]
B. It is a Silverlight application requiring a browser plugin on first use.
C. It is a Java applet that downloads a local client at each login.
D. It is a native Windows application installed through the Microsoft Store.
Correct Answer: A
Rationale: The 3CX Web Client is built natively on HTML5 and JavaScript, so any modern supported browser (Chrome,
Edge, Firefox) can run it without plugins, add-ons, or downloads. Legacy plugin-based architectures such as Silverlight or Java
applets are precisely what 3CX moved away from in v20. This design is also what enables WebRTC-based calling directly from
the browser. Describing it as a Store-installed native application confuses the Web Client with the 3CX desktop App.
Q8: Which browser is NOT supported for use with the 3CX Web Client?
A. Google Chrome
B. Microsoft Edge
C. Mozilla Firefox
D. Internet Explorer 11 [CORRECT]
Correct Answer: D
Rationale: 3CX supports the modern evergreen browsers Chrome, Edge, and Firefox for the Web Client. Internet Explorer 11
is a legacy browser without the WebRTC and modern JavaScript support the client requires, so it is not supported. Attempting
to use IE11 typically produces broken login pages and no audio path for WebRTC calls. Chrome, Edge, and Firefox are all
validated on both desktop operating systems 3CX supports.
3CX Basic Certification Exam Prep - VoIP PBX System Administration Page 4 of 44
