Understanding OpenVPN: A Versatile Virtual Private Networking Solution

I. Introduction to OpenVPN

OpenVPN is a robust open-source software application for establishing secure point-to-point and site-to-site connections for virtual private networking. Originally created by James Yonan in 2001, OpenVPN offers a highly customizable VPN solution that can be deployed across various platforms and environments.

At its core, OpenVPN enables creating encrypted tunnels between configured endpoints – whether linking two client devices peer-to-peer or bridging entire remote office LAN segments together over the internet securely. Traffic traversing OpenVPN tunnels sees encryption wrapping sensitive data while also benefiting from authentication checks.

This makes OpenVPN suitable for use cases ranging from mobile user secure access needs all the way up to site-to-site VPN connectivity rivaling expensive Cisco enterprise solutions. The open nature and continual advancement by an engaged development community also helps OpenVPN remain a versatile secure networking utility.

Below we explore essential OpenVPN features and capabilities that have positioned it as a virtual private networking tool of choice for everyone from individual consumers up to businesses and even app developers looking to embed VPN-style functionality into their own products.

II. Features of OpenVPN

OpenVPN’s capabilities can be viewed through both its open source core offering as well as the commercial OpenVPN Access Server product built atop the open variant. Each provides useful features.

OpenVPN Access Server Features

The OpenVPN Access Server adapts and expands upon opens source OpenVPN 2.0 to add enterprise-ready capabilities like:

• Simple centralized management with fore modules and tools
• Scalable licensing tiers to support more simultaneous connections
• Clustered and cloud deployment options
• Enhanced security protections beyond vanilla OpenVPN

This delivers a turnkey software VPN solution allowing small to large organizations deploy their own managed OpenVPN infrastructure with enhanced controls ready for growing business needs.

Flexibility, Scalability and Packed with Features

OpenVPN Access Server gives IT administrators extensive controls for configuring and customizing virtual private access balanced against usability needs, available infrastructure and budget considerations across licenses supporting from 5 up to thousands of concurrent VPN connections from users andbranch locations. Identity services integration and plugin frameworks also enable adapting platforms to specialized requirements.

Robust traffic management, access control policies and built-in redundancy options bolster the solution’s flexibility to align with shifting usage patterns and organizational needs.

Access Control Rules and Redirection Options

From an access management perspective, Access Server gives admins concrete ways to dictate authentication requirements along with whether to enable full tunnel or split-tunnel OpenVPN connections from particular user groups. This helps segment what resources get exposed over the VPNs along with preventing unauthorized connectivity from unknown devices.

Access rules configurations also support rich policies routing users to particular VPN endpoints based on factors like user group membership, specific application flows, targeted URL categories, individual MAC addresses and more. These controls get reinforced by ancillary addons to enable bandwidth metering, blocking via DNS blackhole lists and script execution too.

Professional Services and Automated Certificate Lifecycle Help Too

For organizations lacking specialized networking and security skills running virtual private network environments at scale, OpenVPN even offers professional services packages to accelerate deployment with expert-led configuration guidance and knowledge transfer. This gives internal IT teams the tools and knowledge for self-sufficient management moving forward.

OpenVPN Access Server also automates traditionally manual tasks like issuing and renewing the cryptographic certificates underpinning trusts in the VPN connectivity. Automated expiration notices and simplified mass reissuance prevents certificate authority legitimacy issues cropping up and breaking connectivity across endpoints relying on the VPN services.

Cloud VPN Features

Increasingly OpenVPN gets deployed across infrastructure hosted by public cloud platforms like AWS, Azure and Google Cloud. OpenVPN Cloud brings purpose-built enhancements for these environments including:

• Tight integration with native cloud identity management
• Leveraging cloud scale/resiliency innately
• Optimized usage and licensing costs fit cloud economics
• Consistent configurations across regions/data centers
• APIs expand custom tooling potential

Dedicated Private Overlay Networking

OpenVPN Cloud provides overlay network connectivity across VPCs and cloud data centers reflecting centralized VPN policy administration while preventing security groups conflicts. This enables securely bridging cloud resources without messy site-to-site IPsec complexities.

Restrict and Filter Internet Access

Wrapping cloud instance internet access through OpenVPN Cloud gateways allows controlling traffic visibility tighter. Cloud VPN filtering gives means to restrict outbound connectivity via rules blocking URL categories, protocols and ports – delivering important governance otherwise missing from cloud IaaS networking flexibility.

Secure Scalability for IoT and Mobile

The cloud friendly nature also suits needs of mobility and internet infrastructure providers needing to embed security in consumer offerings where scale demands paying only for actual usage can work better than fixed licensing costs of classic Access Server. This makes OpenVPN Cloud a choice for WiFi hotspot security, mobile carriers and even securing streams from vast solar inverter and IoT deployments.

Flexible Internet Routing

Software defined network policies available through OpenVPN Cloud help companies take firmer control over cloud traffic routing to inspect flows without impacts, shift directions based on characteristics like user identity and better isolate sensitive system access functionally despite cohabiting cloud environments posing administrative barriers typically. Defining secure VPN policy overlays restores important controls.

OpenVPN Access Server Advantages

Stepping back, multiple advantages position OpenVPN Access Server as an appealing enterprise VPN proposition beyond just its OpenVPN core.

Based on Proven, Open Source Software

Unlike some SSL VPN appliances, OpenVPN Access Server builds capabilities atop the widely scrutinized open source OpenVPN 2.x foundation for its core tunnel functionality. This brings an engagement community continuously optimizing and hardening the offerings’ security posture.

Granular Challenge/Response Authentication Options

related, Access Server integrates tightly with systems like RADIUS and LDAP for enterprise identity and authentication systems to flexibly enforce dynamic multifactor and adaptive requirements before granting VPN access. This expands controls beyond just simple VPN tunnel establishment.

Centralized Management and Single Sign-On Integration

Via plugin frameworks and published APIs, OpenVPN Enterprise integrates both with major identity management suites from Microsoft and Linux ecosystems to enable single sign-on aligned user experiences. Meanwhile OpenVPN’s own centralized management dashboard streamlines controlling user policies, pooling licenses and monitoring certificate lifecycles across dispersed endpoints.

Secure Remote Script Execution

Unique extras like arbitrary script execution after successful user authentication inside the VPN session help safely enable proprietary system management flows across remote endpoints without exposing them openly. This offers routes to consolidate tools leveraging existing user identities and access permissions.

Spanning both the open community backed platform origins along with commercially supported enterprise management suites for larger deployments, OpenVPN checks important boxes around security, authentication, flexibility and scalability that organizations demand from business-critical virtual private networking infrastructure solutions in the modern era.

III. Setting Up OpenVPN

While OpenVPN Access Server simplifies deployment and management considerably, individual users or technology teams can still locally configure and manage OpenVPN 2.x community software themselves. This offers both client-based VPNs along with site-to-site networking.

Configuring Client/Server VPNs

The quickstart guide below sets up a basic yet fully working tunnel between an OpenVPN server and client peer:

On the Server

1. Install OpenVPN and EasyRSA utilities
2. Initialize the certificate authority
   • ./easyrsa init-pki
3. Generate the master secret signing certificate
   • ./easyrsa build-ca
4. Generate server certificate and key
   • ./easyrsa build-server-full [server_name] nopass
5. Generate Diffie-Hellman key
   • ./easyrsa gen-dh
6. Configure server by copying key/certificate files into /etc/openvpn/server and editing server config file
   • /etc/openvpn/server.conf
7. Make sure networking allows IP forwarding between interfaces
8. Start OpenVPN server process
   • systemctl start openvpn@server

On Each Client

1. Install OpenVPN
2. Transfer easyrsa CA certificates from server required for trusting connection
3. Generate client certificate and key
   • ./easyrsa build-client-full [client_name] nopass
4. Configure client by copying certificates into /etc/openvpn/client
   • Update /etc/openvpn/client/client.conf file
5. Connect!
   • sudo openvpn /etc/openvpn/client/client.conf

This outlines the fundamentals – further customization allows bridging to internal networks, using alternative authentication methods and hardening security further.

OpenVPN Server Setup on Ubuntu 20.04

Specific Ubuntu server instructions help create a hardened infrastructure OpenVPN endpoint accessible from remote client peers:

Server-Side Setup

1. Install
   • apt install openvpn easy-rsa
2. Initialize PKI
   • make-cadir ~/openvpn-ca
   • cd ~/openvpn-ca
   • source vars
   • ./clean-all
3. CA certificate
   • ./build-ca
4. Server cert
   • ./build-key-server server
5. Generate Diffie-Hellman key
   • ./build-dh
6. Configure
   • Copy files to /etc/openvpn/server
   • Edit /etc/openvpn/server.conf
7. Start service
   • systemctl start openvpn@server

Client Configuration

1. Install
   • apt install openvpn
2. Get CA, certs and keys
   • Transfer from server ~/openvpn-ca/keys
3. Edit client config
   • /etc/openvpn/client/client.conf
4. Connect!
   • sudo openvpn /etc/openvpn/ client/client.conf

This provides a template for getting started with OpenVPN setup on Ubuntu systems, offering clients encrypted access into the private network.iptables rules and tighter cert/cipher policies lock things down further.

IV. OpenVPN Source Code

As open source software, OpenVPN offers full transparency and community reviewability across various repos:

OpenVPN 3 Linux – Next gen Linux kernel integrations for VPN support

OpenVPN Connect – Mobile/desktop client apps to access OpenVPN environments

OpenVPN 3 Core – Underlying cross-platform libraries and core engine

Continual development by maintainers and sponsors ensures the software keeps advancing with ever stronger algorithms, more efficient code and heightened security. Open source DNA encourages this.

V. OpenVPN Access Server Configuration

The commercial OpenVPN Access Server solution offers extensive customization parameters across:

User Management

• External identity provider integration
• Granular user permission policies
• MAC address tracking/policy controls

VPN Functionality

• TCP vs UDP tunnel options
• Routing methods like NAT vs direct layer 2
• IPv4/IPv6 handling policies
• Split tunneling controls

Infrastructure

• Static endpoints vs dynamic discovery
• Redundant VPN gateways
• Regional server selection options

Particularly around infrastructure configuration, Access Server provides optimization potential around:

Dynamic IP Assignment

The built-in DHCP server issuing private IPs to connecting clients offers flexibility toggling between static allocations via MAC to reservation through dynamic pools where IPs get assigned from ranges only when actively in use.

Routing Method

Access Server supports routing traffic through gateway VPN servers with NAT layers or enabling full layer 2 connectivity passed through the tunnels for inter-site bridging absent these extra hops.

Split Tunneling Choices

Granular options exist to enforce full tunnel encryption across all traffic from client devices vs only capturing particular flows with split tunneling that allows normal internet access simultaneously alongside VPN connectivity.

The breadth of customization points enable tailoring Access Server deployments to the needs and policies of a given organization.

OpenVPN Access Server Status Overview

Besides monitoring logs and dashboards plots showing live traffic and user trends, the Status:Overview page in Access Server Manager provides a fantastic centralized snapshot outlining configuration details, user licensing usage metrics and server health indicators important for ongoing management visibility:

This singular view captures so much critical detail needed when administering the platform helping pinpoint any issues needing investigation without hopping between dozens of individual pages constantly.

Conclusion

From individual remote access needs up through site-site infrastructure demands and even enabling secure connectivity for cloud workloads, OpenVPN delivers versatile open source backed virtual private networking utilities.

The OpenVPN Access Server commercial offering expands the secure networking platform for enterprises requiring identity federation, granular access controls, licensing management plus automated lifecycle tooling across private VPN endpoints.

With software builds supporting extensive OS platforms and customization capacity unlocking niche use case potential, OpenVPN continues maturing as a robust networking option for shielding data transfers and system access with encrypted VPN tunnels checked against centralized policies.

Whether self-deployed or via hosted services, OpenVPN flexibility enables dialing in protections aligned with risks – individual remote access needs differ from office site connectivity after all. Encrypted channels safeguard flows while remaining lightweight compared to protocols like IPSec.

From consumers to devops engineers and enterprise IT admins, OpenVPN empowers technical teams across organization sizes to take hold of networking security. Versatility across porting code variants plus configuration options to fine tune behaviors for particular environments position the software suits to handle swelling usage securing modern mobility and infrastructure demands at scale.