Dual-SIM 4G Failover and Shared Failure Risks

Identify shared components

Determine whether the router has one modem or multiple active modems. List shared power, antennas and upstream infrastructure. Different SIM brands may still share network dependencies, so do not equate two subscriptions with complete independence.

Test meaningful failure conditions

Test loss of registration, failed internet reachability and an unavailable application endpoint separately. Choose health checks that detect the intended fault without switching networks merely because one optional server is down. Record detection time and reconnection time.

Check application continuity

Verify buffered data, VPN recovery and duplicate handling after the address changes. Test return to the preferred SIM and guard against repeated switching. Keep local operations safe and useful while failover is in progress.

FAQ

Technical References

• Teltonika: Dual-SIM support