Answer
The Chassis MIB (jnxchassis.mib) displays the hardware and chassis details for each Juniper Networks device. It provides information about the router and its components. The Chassis MIB objects represent each component and its status.
You can query the Chassis MIB objects jnxOperatingMemory, jnxOperatingtBuffer, and jnxOperatingCPU to determine the CPU and memory utilization of the hardware components (Routing Engine, FPC, and PIC) of a device.
For a list of supported standard and enterprise-specific MIBs, click SNMP MIBs and Traps Reference