Load balancing is the distribution of network traffic across multiple connections, either to increase total available capacity or to spread risk across independent paths. It is the counterpart to failover: where failover uses a backup only when the primary fails, load balancing uses multiple connections simultaneously.

In short: Industrial routers typically support several load balancing modes. Round-robin distribution sends successive connections out of different WAN links. Weighted distribution favours the faster or cheaper link, with overflow to a secondary. Policy-based routing sends specific traffic types (CCTV, telemetry, voice) over specific links based on rules. Bonding (a more advanced technique, often via third-party software such as BONDIX, Speedify, or Peplink) combines multiple cellular links into a single virtual connection with aggregated bandwidth.

For most IoT deployments, simple policy-based load balancing is enough. Send CCTV uplink over the cellular SIM with the larger data plan, send corporate management traffic over the fixed line, and let standard internet usage take whichever link has spare capacity.

Bonded cellular becomes worthwhile in mobile applications (broadcast vehicles, emergency response, public-transport Wi-Fi) where one cellular link's capacity is not enough and packet-level bonding across multiple SIMs gives smoother performance than per-flow balancing. The Teltonika RUTM52 supports BONDIX for this kind of deployment.