In today’s connected world, relying on a single internet connection can be risky. Whether in a small office, educational environment, or smart home setup, internet outages can disrupt workflows, communication, and services.

With OPNsense, a powerful free and open-source firewall platform, it’s possible to configure multi-WAN failover and load balancing, ensuring high availability and improved performance—without the cost of proprietary systems.

🔓 What is OPNsense?

OPNsense is a fully featured, open-source firewall and routing platform based on FreeBSD. Developed by Deciso and supported by a global community, it provides enterprise-level networking capabilities to individuals, businesses, and institutions for free.

Key features include:

• Firewall, NAT, and traffic shaping
• VPN support (IPsec, OpenVPN, WireGuard)
• Intrusion detection and prevention
• VLANs, IPv6, and DHCP/DNS services
• Multi-WAN failover and load balancing
• Plugin system for added functionality (HAProxy, Zabbix, ntopng, etc.)

OPNsense includes an intuitive web-based GUI, making advanced network configurations accessible even to non-experts.

🌐 Why Multi-WAN?

Multi-WAN refers to using two or more internet connections simultaneously. This improves both reliability and bandwidth efficiency.

There are two common use cases:

1. Failover – Provide redundancy if one ISP goes offline.
2. Load Balancing – Distribute traffic across multiple links to maximize bandwidth usage and reduce latency.

Both are configurable in OPNsense using built-in tools, requiring no third-party software.

🔁 Failover: Automatic Internet Redundancy

Failover ensures automatic switching to a backup connection when the primary WAN goes offline.

How Failover Works in OPNsense:

• Each WAN interface is assigned a gateway.
• A Gateway Group is created with priority tiers (e.g., Tier 1 for primary, Tier 2 for backup).
• OPNsense monitors the health of each WAN using DPinger (ICMP ping to a stable external IP such as 8.8.8.8).
• If the primary WAN fails (e.g., due to packet loss or high latency), OPNsense routes traffic to the backup WAN.
• When the primary connection recovers, routing automatically returns to the preferred gateway.

Failover is commonly used in businesses, retail stores, or any environment where internet uptime is critical.

⚖️ Load Balancing: Optimizing Bandwidth Usage

Load balancing allows distribution of outbound traffic across multiple internet links.

How Load Balancing Works:

• Multiple WAN interfaces are added to the same Gateway Group with equal tier levels (e.g., both set to Tier 1).
• OPNsense uses round-robin routing to assign new connections across the available gateways.
• This improves overall bandwidth availability and user experience during peak usage times.

Note: Individual TCP/UDP sessions are not split between WANs. Load balancing works on a per-connection basis.

This setup is ideal for shared office networks, multi-user households, and public Wi-Fi deployments where internet usage varies widely.

🧰 Example Configuration Scenarios

1. Basic Failover Setup

• Primary WAN: Fiber broadband (Tier 1)
• Secondary WAN: LTE modem (Tier 2)
• Result: Internet automatically switches to LTE during fiber outages.

2. Load Balanced Setup

• WAN1: 100 Mbps fiber
• WAN2: 50 Mbps DSL
• Configuration: Both set to Tier 1 in a Gateway Group
• Result: New connections are distributed between the two links, improving throughput.

3. Hybrid Setup

• Create multiple Gateway Groups:
  • One for general traffic (load balanced)
  • One for VoIP or VPN (failover only)
• Use firewall rules to apply specific Gateway Groups based on traffic types or source networks.

✅ Best Practices for Multi-WAN on OPNsense

• Monitor IPs: Use reliable external IPs (e.g., 1.1.1.1 or 8.8.8.8) for WAN monitoring.
• Sticky Connections: Enable to maintain session stability (useful for banking, video conferencing).
• DNS Configuration: Use the DNS Resolver with custom forwarding to prevent DNS leakage or loopback issues.
• Firewall Rules: Explicitly define routing per traffic type or VLAN to make full use of multiple WANs.

🧾 Summary

OPNsense enables users to build a robust, cost-effective, and enterprise-grade network using entirely free and open-source tools. Its multi-WAN functionality provides reliability and flexibility that rivals commercial products—making it a powerful choice for modern networking needs.

🔗 Further Reading

• OPNsense Multi-WAN How-To Guide
• OPNsense Official Website
• FreeBSD Project – The operating system OPNsense is built on