Asterisk is a powerful open-source VoIP (Voice over Internet Protocol) platform that enables you to set up your own telephony server for tasks like call routing, conferencing, and voicemail. This guide explains how to install and configure Asterisk on your VPS.

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Why Choose Asterisk for VoIP?

• Highly Customizable: Asterisk allows for intricate call handling and routing.
• Open Source: No licensing fees for basic functionalities.
• Feature-Rich: Supports PBX systems, IVRs, and more.
• Scalable: Suitable for small businesses and large enterprises alike.

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Prerequisites

1. VPS: A Linux-based VPS (Ubuntu or CentOS preferred).
2. Root Access: Required for installation.
3. Updated System: Ensure your VPS is updated with the latest packages.

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Step 1: Update Your System

Start by ensuring your server is up to date:

For Ubuntu/Debian:

For CentOS:

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Step 2: Install Required Dependencies

Install tools and libraries required for Asterisk:

For Ubuntu/Debian:

For CentOS:

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Step 3: Download and Compile Asterisk

1. Navigate to your working directory:

    

   cd /usr/src

2. Download the latest version of Asterisk:

    

   wget http://downloads.asterisk.org/pub/telephony/asterisk/asterisk-20-current.tar.gz

3. Extract the downloaded file:

    

   tar -xzvf asterisk-20-current.tar.gz cd asterisk-20.*

4. Install additional build dependencies:

    

   sudo contrib/scripts/install_prereq install

5. Configure and compile Asterisk:

    

   ./configure make menuselect
   • In the menuselect interface, enable desired modules such as CORE-SOUNDS-EN (English sound prompts).
   • Exit and save changes.

6. Build and install Asterisk:

    

   make sudo make install sudo make samples sudo make config sudo ldconfig

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Step 4: Configure Asterisk

1. Start the Asterisk Service

Enable and start the service:

2. Verify Installation

Access the Asterisk CLI (Command Line Interface):

You should see the Asterisk CLI prompt (*CLI>).

3. Set Up SIP Extensions

Edit the SIP configuration file:

Add the following for two test users:

4. Set Up Dial Plan

Edit the extensions.conf file to define how calls are handled:

Add the following:

Reload Asterisk configuration:

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Step 5: Open Firewall Ports

Ensure your VPS allows traffic on VoIP-related ports:

For ufw (Ubuntu/Debian):

For firewalld (CentOS):

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Step 6: Test Your VoIP Server

1. Install a softphone application on your PC or mobile device (e.g., Zoiper or Linphone).
2. Configure the softphone to connect to your Asterisk server:
   • SIP Username: 1001 or 1002.
   • Password: As defined in sip.conf.
   • Server Address: Your VPS's public IP.
3. Make a test call between extensions to confirm the setup.

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Optional: Secure Your VoIP Server

1. Use Strong Passwords: Avoid easy-to-guess SIP passwords.
2. Enable Fail2Ban: Protect against brute force attacks.
    

   sudo apt install fail2ban -y
   Configure it to monitor Asterisk logs (/var/log/asterisk/messages).
3. Use TLS and SRTP: Encrypt SIP traffic for additional security.

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Conclusion

By following this guide, you’ve successfully installed and configured a VoIP server with Asterisk on your VPS. This setup can handle simple call routing or scale to more complex scenarios as your needs grow. Explore Asterisk’s documentation for advanced features like IVR, voicemail, and call queues.