Dual internet links: how to get real failover, not just two bills.

Many offices pay for two internet connections and still go offline together. Redundancy needs more than a second contract.

Check the paths

If both providers’ cables share a duct or a local exchange, a single dig takes out both. Ask for separate physical routes where possible, or mix technologies: fibre plus fixed wireless, or fibre plus 5G.

Choose the right equipment

The firewall or router must support dual-WAN with health checks. It should test each link, not just see that the port is up, and switch when the link stops carrying traffic.

Decide the mode

• Active-passive: a backup link takes over on failure.
• Active-active: both carry traffic, with load sharing, and either can take the whole load.

Think about the applications

Public IP addresses change when you fail over, which can break inbound services and VPNs. Plan for dynamic DNS, BGP with your own addresses, or SD-WAN to keep sessions alive.

Power and everything else

A second link is no use if the switch or router loses power. Put the edge equipment on a UPS.

Test it

Unplug the main link in a controlled window. Watch how long the cutover takes, what breaks and how users notice. Document the result and repeat the test regularly.