Simplifying Multi-WAN Site-to-Site VPNs: Overcoming Complexity with flexiWAN

Why Is Configuring Traditional Site-to-Site VPNs So Complex?

When connecting two sites with dual WANs - one with a public IP and the other behind NAT or CGNAT - several technical obstacles make the process frustratingly complex:

1. Lack of NAT Traversal Support Traditional VPN solutions (e.g., IPsec or OpenVPN) generally require at least one side of the connection to act as a VPN server. This demands a public IP for the server to accept incoming connections and static routing and port forwarding configurations for stability. When a WAN is behind CGNAT, the interface cannot function as a VPN server. The private IP and shared public address assigned by the carrier block incoming requests from reaching the VPN server. The NATed WAN is forced into a client-only role, creating a one-way dependency on the public-IP WAN to maintain connections. Without NAT traversal techniques like STUN (Session Traversal Utilities for NAT) or ICE (Interactive Connectivity Establishment), setting up tunnels becomes an uphill battle.
2. Bi-Directional Failover Complexity Dual WAN setups are designed for redundancy, but ensuring that both WANs can failover seamlessly is extremely difficult with traditional solutions. Each site must configure VPN servers and clients for both WANs, and routing must dynamically update to reroute traffic when either WAN fails. These updates require custom scripts or third-party tools to ensure the VPN can reconnect through the backup WAN. This setup demands two site-to-site VPN tunnels per WAN pair, leading to four tunnels for bi-directional failover. Managing and testing failover across multiple tunnels introduces significant overhead. Misconfigurations in routing or tunnel prioritization can lead to downtime or broken connections.
3. Manual Configuration Overload Traditional solutions rely heavily on manual configurations, which must be repeated for every site. This includes defining VPN servers, clients, and routing tables, adding NAT rules and static routes to allow traffic through NATed interfaces, and testing and troubleshooting for edge cases, such as when both primary WANs fail simultaneously. Even experienced network engineers find these processes time-consuming and error-prone. Scaling this setup to multiple sites compounds the problem, leading to an overwhelming amount of configuration work.
4. Dynamic WAN IP Addresses In many cases, backup WANs (like LTE connections) have dynamic IPs that change frequently, further complicating VPN setups. Traditional solutions require Dynamic DNS (DDNS) services to map changing IPs to a hostname and continuous updates to routing and tunnel configurations to account for IP changes. Dynamic IP handling adds another layer of dependency and potential points of failure. Recovery after failover is often delayed, as the VPN must reestablish connections after IP updates.
5. No Unified Management Managing multiple tunnels across dual WANs with public and private IPs requires juggling several tools and interfaces. There’s no single pane of glass to oversee tunnel health and status, failover performance, or dynamic updates for routing and policies. Without centralized management, monitoring and troubleshooting become labor-intensive, and errors in one site’s configuration can propagate across the network, leading to cascading failures.

How flexiWAN Solves Site-to-Site VPN Challenges

With flexiWAN, the complexities of setting up a reliable, failover-ready site-to-site VPN are eliminated. The same dual WAN setup transforms into a seamless, automated solution:

1. Built-In NAT Traversal flexiWAN integrates NAT traversal technologies like STUN, enabling secure tunnels even when both WANs are behind NAT or single side CGNAT. Unlike traditional VPNs, flexiWAN does not require public IPs or port forwarding. Both WANs can act as active participants in the VPN connection, and failover works smoothly without additional configuration.
2. Automated Tunnel Management With flexiWAN, tunnels are created and managed automatically through flexiManage, the central cloud-based management platform. Only a few clicks are needed to connect two sites, regardless of the WAN configurations. flexiWAN handles all routing, NAT traversal, and failover logic dynamically. This eliminates the need for manual VPN server or client configurations, reduces deployment time from hours (or days) to minutes, and enables centralized management of multiple devices, whether it’s a handful or thousands.
3. Application-Based Routing – Path Selection flexiWAN enables application-based routing and path selection, allowing traffic to be routed dynamically based on the application type, priority, or performance requirements. This feature optimizes network utilization by ensuring that critical traffic takes the best available path. High-priority traffic like VoIP or video conferencing gets routed through optimal paths, reducing latency and improving overall network performance.
4. AI-Powered Failover flexiWAN’s Network Healing feature detects connectivity issues in real-time and reroutes traffic through the secondary WAN instantly. This works even if the secondary WAN is behind CGNAT. Continuous uptime is maintained without manual intervention, proactively resolving potential network problems.
5. Scalability Without Complexity Whether managing two sites or two thousand, flexiWAN provides a consistent, scalable solution. It enables centralized, cloud-based management of tunnels and policies across all devices and makes automatic adjustments for dynamic IPs and NAT conditions. Adding new sites becomes effortless, and network performance and tunnel health are always visible.

Check out below video to learn how easy is to deploy multiple flexiWAN devices and set up tunnels across multiple WAN's, in just a few minutes and clicks.

Conclusion

Traditional site-to-site VPN setups are complex, time-consuming, and ill-suited for modern networking needs, especially with dual WAN configurations involving NAT or CGNAT. With flexiWAN, these challenges are a thing of the past. By automating NAT traversal, tunnel creation, failover, offering cloud-based centralized management, and introducing application-based routing, flexiWAN transforms the way organizations deploy and manage their site-to-site VPNs. What once took hours of manual effort can now be achieved in just a few clicks, with the added reliability of AI-driven network healing.

Get Started Today

Experience how flexiWAN simplifies your multi-WAN site-to-site VPN deployments. Visit our website or schedule a demo to see the difference!