Understanding Dual WAN Failover and Load Balance

Dual WAN failover

Dual WAN failover is a network redundancy solution that switches to a secondary WAN connection to ensure uninterrupted Internet connectivity when the primary connection fails. This technology is particularly important for organizations and users who rely on the Internet for critical tasks such as data transfer, communication, and transactions.

Benefits of dual WAN failover

Increased network reliability

Dual WAN failover ensures that you stay connected to the Internet even if your primary Internet connection fails. This feature is especially important for users who require continuous Internet connectivity to operate.

Automatic failover

Dual WAN failover provides automatic failover to the secondary WAN connection when the primary connection fails. This feature ensures that your network stays online with minimal interruption.

Customizable failover policy

Dual WAN failover allows you to customize the failover policy to suit your needs. You can adjust the detect interval and trigger condition for better experience.

Limitations of dual WAN failover


If a dedicated network is prepared for dual WAN redundancy, it will increase the cost. If it is a temporary requirement, iPhone/Android phone can be connected to the ASUS router USB to serve as backup network.


Limited bandwidth

Dual WAN redundancy cannot provide a way to combine the bandwidth of both connections. The maximum bandwidth is limited to the primary or secondary connection, depending on which one is active.

For the requirement of uninterrupted internet connection, dual WAN redundancy is a critical solution. When the primary network connection fails, it will automatically switch to the function of the secondary network connection to ensure uninterrupted network service. Before implementing this solution, the cost and complexity of implementing it need to be considered. If your router has a USB, you can connect your phone for testing first.

Dual WAN load balance

Dual WAN load balancing is a technology that distributes network traffic across two internet connections to improve network availability.

Benefits and drawbacks of dual WAN load balance

The benefits of using dual WAN load balancing include improving network availability. When users want to improve network availability and performance by distributing network traffic across two internet connections, dual WAN load balancing is a good option to suggest. It can be used when one connection is unreliable or when certain applications or services require a specific ISP connection for optimal performance.

However, using dual WAN load balancing also has some limitations:

Inability to use hardware network acceleration

Generally, the hardware acceleration feature of routers can only use a single external IP, so routers will disable the hardware acceleration feature in load balancing mode.

Complex setup

Dual WAN load balancing may be difficult to set up and requires a certain level of technical expertise. Configuring and managing two internet connections can be challenging.

Uneven traffic distribution

It is possible that one internet connection is heavily used while the other is idle. This may lead to uneven traffic distribution, which can reduce the effectiveness of load balancing.

Compatibility issues

Some applications may not be compatible with dual WAN load balancing and require specific network configurations or settings.

In conclusion, dual WAN load balancing can be an effective way to improve network performance and availability, but it requires careful planning and management to ensure the best results. If the primary connection is stable and has sufficient bandwidth, it is not recommended to use dual WAN load balancing.

Q: Why can’t we expect dual WAN load balancing to combine the bandwidth of two internet connections? For example, 100Mbps + 400Mbps does not equal 500Mbps bandwidth.

A: Dual WAN load balancing can distribute network traffic across two internet connections, but it cannot combine the bandwidth of these connections. In other words, each individual connection can only provide its maximum speed, so the total speed will be limited by the maximum speed of each individual connection.

In your case, the maximum speed you can achieve through dual WAN load balancing is 400Mbps because this is the maximum speed of your faster internet connection. However, the actual speed you achieve will depend on the load balancing algorithm used and how network traffic is distributed across the two connections.

Q: What features do not work properly on the secondary WAN in dual WAN load balancing?

A: In a dual WAN load balancing configuration, DDNS, virtual server port forwarding, VPN server, AiProtection, QoS, and more cannot work properly on the secondary WAN interface.

This is because DDNS relies on the primary WAN’s public IP address to associate domain names with specific network locations. The IP address associated with the domain name on the secondary WAN does not match the public IP address of the primary WAN interface, so it cannot work on the secondary WAN.

Port forwarding also relies on a fixed public IP address to forward traffic to specific internal IP addresses and ports. If the secondary WAN interface is used as the primary interface, port forwarding rules may not work properly because the public IP address associated with the secondary WAN interface may not match the expected IP address of incoming traffic.

Similarly, VPN server, AiProtection, and QoS all depend on the primary WAN, so these features cannot work on the secondary WAN.

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