Dual-WAN Failover: Keeping Your Office Online

For many businesses, an internet outage now means billing stops, cloud applications freeze and customer calls go unanswered. A single fiber cut or equipment fault can cost far more than a backup link would have. Dual-WAN failover is the most practical way to stay online.

How dual-WAN works

A dual-WAN router connects to two separate internet links — for example, a primary fiber line and a secondary broadband or 4G/5G connection. The router continuously checks the health of each link. If the primary fails or degrades, traffic moves to the secondary automatically, usually within seconds.

Failover vs load balancing

• Failover: the backup link sits idle until the primary fails.
• Load balancing: both links carry traffic at the same time, with sessions shared between them. If one fails, the other carries everything.

Many businesses use load balancing for general browsing and failover for sensitive applications.

Choose truly diverse links

Two connections from the same provider over the same cable route can fail together. Ideally choose different providers, different physical paths or a different technology such as wireless for the backup.

Health checks that reflect reality

Good routers test more than whether the cable is plugged in. They check reachability of external servers, latency and packet loss, so a link that is up but unusable triggers failover too.

Plan for what fails over

Inbound services like a hosted website or remote access need planning, as the backup link has a different IP address. Dynamic DNS or cloud-based services help.

Test regularly

Unplug the primary link during a quiet period every few months to confirm failover works as expected.

The bottom line

Dual-WAN failover turns a business-stopping outage into a minor slowdown. A managed router with diverse links is one of the best resilience investments a business can make.

Learn more about Managed Router & SD-WAN from UbiFi, or talk to our team.