6.3 OpenVPN Explained

Key Concepts

• OpenVPN Overview
• OpenVPN Components
• OpenVPN Configuration
• Security Features
• Troubleshooting Tips

1. OpenVPN Overview

OpenVPN is an open-source VPN (Virtual Private Network) solution that allows secure communication over public networks. It uses a custom security protocol that utilizes SSL/TLS for key exchange. OpenVPN is highly configurable and can run on various platforms, including MikroTik routers.

Example: Think of OpenVPN as a secure tunnel that allows data to travel safely between two points, even if the path is through a public and potentially unsafe area.

2. OpenVPN Components

OpenVPN consists of several key components:

• OpenVPN Server: The central server that manages VPN connections and routes traffic.
• OpenVPN Client: The end-user device that connects to the OpenVPN server to establish a secure connection.
• Certificate Authority (CA): A trusted entity that issues digital certificates for authentication.
• Digital Certificates: Files used to authenticate the identity of the server and clients.
• Configuration Files: Text files that define the settings and parameters for the OpenVPN server and clients.

Example: Consider the OpenVPN server as a secure office, the clients as employees, the CA as a security guard, and the certificates as employee badges. The configuration files are the rules that govern how employees can enter and exit the office.

3. OpenVPN Configuration

Configuring OpenVPN involves setting up the server, generating certificates, and creating configuration files. Key steps include:

• Install OpenVPN: Download and install the OpenVPN software on the server and client devices.
• Generate Certificates: Use the OpenVPN easy-rsa scripts to create a CA and issue certificates for the server and clients.
• Configure Server: Create a server configuration file that defines the network settings, encryption methods, and authentication requirements.
• Configure Clients: Create client configuration files that match the server settings and include the client's digital certificate.

Example: Configuring OpenVPN is like setting up a secure office. You need to install security systems (OpenVPN software), issue employee badges (certificates), and define the rules for entering and exiting (configuration files).

4. Security Features

OpenVPN offers several security features to protect data:

• Encryption: Uses strong encryption algorithms like AES to protect data in transit.
• Authentication: Uses digital certificates and optional user credentials to verify the identity of the server and clients.
• Data Integrity: Ensures that data has not been tampered with during transmission using hash functions like SHA.
• Perfect Forward Secrecy (PFS): Generates a new key for each session, ensuring that even if a key is compromised, past sessions remain secure.

Example: Think of OpenVPN's security features as layers of protection for a package. Encryption is like wrapping the package in a secure material, authentication is like adding a lock with a unique key, data integrity is like adding a seal, and PFS is like changing the lock for each delivery.

5. Troubleshooting Tips

Troubleshooting OpenVPN issues can involve several steps:

• Check Logs: Review the OpenVPN server and client logs for error messages and warnings.
• Verify Certificates: Ensure that the certificates are correctly generated and installed on both the server and clients.
• Network Configuration: Verify that the network settings, such as IP addresses and routes, are correctly configured.
• Firewall Settings: Ensure that the necessary ports (e.g., UDP/1194) are open and not blocked by firewalls.

Example: Troubleshooting OpenVPN is like diagnosing a problem with a secure delivery system. You need to check the logs (delivery records), verify the certificates (employee badges), ensure the network settings (delivery routes) are correct, and make sure the firewalls (security gates) are not blocking the path.