MX960 Component Redundancy
A fully configured router is designed so that no single point of failure can cause the entire system to fail. Only a fully configured router provides complete redundancy. All other configurations provide partial redundancy. The following major hardware components are redundant:
Host subsystem—The host subsystem consists of a Routing Engine and an SCB. The router can have one or two host subsystems. If two host subsystems are installed, one functions as the primary and the other functions as the backup. If the primary host subsystem (or either of its components) fails, the backup can take over as the primary. To operate, each host subsystem requires a Routing Engine installed directly into in an SCB.
Power supplies—In the AC configuration with normal capacity AC power supplies, a minimum of three power supplies is required to supply power to a fully configured router. All AC power supplies share the load evenly. The addition of a fourth power supply provides full power redundancy. If one power supply fails in a redundant configuration, the three remaining power supplies provide full power. In the DC configuration, AC configuration with high capacity power supplies, high-capacity second-generation AC power supplies, and high-voltage second-generation universal (HVAC or HVDC) power supplies, two power supplies are required to supply power to a fully configured router. One power supply supports approximately half of the components in the router, and the other power supply supports the remaining components. The addition of two power supplies provides full power redundancy. If one power supply fails, the remaining power supplies provide full power to the router.
Cooling system—The cooling system has redundant components, which are controlled by the host subsystem. If one of the fans fails, the host subsystem increases the speed of the remaining fans to provide sufficient cooling for the router indefinitely.