WAN failover behavior

The SC//Reliant™ platform supports automatic failover across up to three WAN connections: a primary, a backup, and an optional tertiary connection — for example, a fiber or broadband primary with LTE/5G cellular configured as backup. This is a general capability of the platform and is not limited to cellular backup specifically.

How failover decisions are made. Each configured connection is checked periodically with reachability tests (ping-based) over its own interface. If the primary connection stops responding, traffic automatically moves to the backup connection. If the backup also fails and a tertiary connection is configured, the platform falls through to that connection next. At any point, if a higher-priority connection becomes reachable again, the platform automatically switches back to it.

Avoiding flapping. After a higher-priority connection recovers, the platform waits briefly before switching back, so a connection that is intermittently dropping in and out doesn't cause repeated back-and-forth switching.

Routing. Routes can be tied to specific WAN interfaces, so which destinations go out which connection updates automatically as the active connection changes — this applies to host routes, network routes, and default routes.

VPN and firewall behavior during a switch. A failover event can be configured to restart VPN tunnels bound to the affected interface, so tunnels re-establish automatically over the new path rather than requiring manual intervention. Firewall rule behavior can likewise be configured to adjust automatically to the active connection.

Visibility. Connection status and failover events are visible to Scale Computing's monitoring, so a switch between primary, backup, and tertiary connections is observable for support purposes. SC//AcuVigil™ provides centralized visibility into WAN status and failover events across the fleet.

Cellular connectivity options

Cellular modem connectivity can be maintained either through an integrated cellular modem service or via an external 4G / 5G modem or router.

Using the Virtual Gateway for connectivity failover

A full connectivity Virtual Network Function (VNF) is available through the SC//AcuVigil™ Virtual Gateway (VG), which delivers a complete firewall, router, VPN, and connectivity solution.

In addition to the reachability-test failover described above, the VG can support failover through any of the following:

Active routing protocols, either Open Shortest Path First (OSPF) or Border Gateway Protocol (BGP).
Virtual Router Redundancy Protocol (VRRP).
Link-state management.

Switchover and fallback are fully automated and configurable.

Workload behavior during a WAN transition

Site-resident workloads such as POS, payment store-and-forward, OT, surveillance, and IoT continue running uninterrupted during a WAN transition, because they do not depend on the WAN at runtime. Cloud-bound traffic, including configuration sync, monitoring telemetry, and central logging, re-routes via cellular within seconds.

Data sync resumes automatically when the primary WAN is restored. Buffered logs and queued events flush in the background with no operator action.

Networking overview — SD-WAN and connectivity-agnostic posture
Networking overview — offline and cloud-edge hybrid behavior

WAN failover behavior

WAN failover behavior