šŸ¦Why Session-Based Load Balancing Breaks Online Banking ā€“ & How Fusionā€™s SD-WAN Fixes ItšŸš€

Ronald BartelsRonald Bartels
3 min read

Multi-WAN setups are essential for businesses looking for better uptime and resilience, but not all load balancing solutions are created equal. Many firewall-based SD-WAN solutions use session-based load balancing, which can cause serious problems for online banking, secure websites, and other session-sensitive applications.

If youā€™ve ever had a banking session randomly disconnect or received a ā€œsession expiredā€ error while making a payment, your firewallā€™s load balancing may be the culprit.


The Problem with Session-Based Load Balancing

Most firewall-based SD-WAN solutions use session-based (or per-flow) load balancing to distribute traffic across multiple links. This means:

šŸ”¹ Each new session is randomly assigned to one of the available WAN links.
šŸ”¹ Subsequent traffic for that session stays on the same link until the session ends.
šŸ”¹ If one link fails, active sessions are dropped because they cannot move between links dynamically.

For many web applications, this method is "good enough", but it completely breaks online banking and secure logins.


Why Online Banking Fails with Session-Based Load Balancing

1ļøāƒ£ Banking Security Detects IP Changes as a Threat

Most online banking platforms and secure websites use strict session security to prevent fraud. They track your IP address at login and expect all future requests to come from the same IP.

šŸ”“ With session-based load balancing, some banking requests (like authentication) may be sent over one ISP, while later requests (like payments) go over another.
šŸ”“ This triggers fraud detection and forces the session to be terminatedā€”resulting in session expiry or re-authentication loops.

2ļøāƒ£ OTP Pages and Payment Gateways Fail Mid-Transaction

šŸ”“ 3D Secure (Verified by Visa / Mastercard SecureCode) relies on tracking your session IP. When session-based load balancing shifts the next request to another ISP, the banking server no longer recognises the session and throws an error.
šŸ”“ This can cause payments to fail or get stuck in an incomplete state.

3ļøāƒ£ Firewall Load Balancers Donā€™t Handle Failover Seamlessly

If one ISP fails during an active banking session, a session-based load balancer cannot move the session to another WAN link. The result?

šŸ”“ The session is lost, and youā€™re logged out.
šŸ”“ You need to start over, re-login, and authenticate again.

For banking, session consistency is critical, and firewall-based SD-WAN solutions fail to deliver.


The Solution | Packet-Based Load Balancing with Fusionā€™s SD-WAN

Fusionā€™s packet-based SD-WAN load balancing avoids all these issues by ensuring:

āœ… Every packet is dynamically assigned the best available WAN pathā€”not just the initial session.
āœ… Session stickiness is maintained when required for banking and secure logins.
āœ… Failover happens in real-time at the packet level, ensuring seamless recovery if a link goes down.
āœ… The banking website sees only one IP address, preventing session expiry issues.

Unlike firewall-based load balancers, Fusionā€™s SD-WAN bonds multiple internet links into a single, stable connectionā€”giving your banking applications the reliability they need.


Why Fusionā€™s SD-WAN is the Rock-Solid Choice

Fusionā€™s SD-WAN doesnā€™t just offer better failover and resilienceā€”it completely eliminates the session-breaking pitfalls of firewall-based SD-WAN solutions.

šŸ”¹ True Multi-WAN Aggregation ā€“ Uses all WAN links at the same time without breaking sessions.
šŸ”¹ Real-Time Packet Steering ā€“ Ensures banking traffic always flows over a single IP.
šŸ”¹ Seamless Failover ā€“ If an ISP fails, the transition is invisible to usersā€”no lost sessions.
šŸ”¹ Smart Routing ā€“ Prioritises mission-critical traffic, like banking, VoIP, and video conferencing.

With Fusionā€™s SD-WAN, online banking just worksā€”no frustrating disconnections, no failed transactions, and no wasted time.


Wrap

Firewall-based SD-WAN solutions break secure banking because they rely on outdated session-based load balancing. This method causes session expiry, login failures, and broken transactions due to IP switching across WAN links.

Fusionā€™s packet-based SD-WAN is the rock-solid solution that keeps online banking stable and seamless. Instead of frustrating errors, users get:

āœ… Consistent connectivity
āœ… Secure, uninterrupted banking sessions
āœ… Smooth, failover-proof transactions

If your business depends on reliable online banking, payments, and other session-sensitive applications, itā€™s time to ditch firewall-based SD-WAN and switch to Fusionā€™s next-generation SD-WAN. šŸš€

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Written by

Ronald Bartels
Ronald Bartels

Driving SD-WAN Adoption in South Africa