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[J] How to view CPU utilization in J Series routers



Article ID: KB11437 KB Last Updated: 05 Sep 2019Version: 9.0

This article provides information about viewing CPU utilization in J Series routers via CLI and SNMP.


Juniper M and T Series routers utilize individual hardware components to cleanly separate operating-system components, which include the Routing Engine, Forwarding Engine, and Services Engine.

However, the J Series platform utilizes a single CPU to handle all three components in the system. It also provides for clean separation of the three components. Each engine has its own protected processing and memory resources, so that processing conflicts are never an issue.

Due to this clean separation, beginning with Junos OS release 8.0, some new commands and SNMP objects were included, specifically for monitoring CPU utilization on the J Series platforms.


For J Series, a single object or command that will show the total CPU usage for both the Routing Engine (RE) and Forwarding Engine combined, is not available. The two components have their own objects to monitor. For the RE, use the show chassis routing-engine command. This command is equivalent to the jnxOperatingCPU SNMP MIB object.

For example:

user@host> show chassis routing-engine   
Routing Engine status:
    Temperature                 26 degrees C / 78 degrees F
    CPU temperature             51 degrees C / 123 degrees F
    DRAM                      2048 MB
    Memory utilization          30 percent
    CPU utilization:
      User                       0 percent
      Real-time threads          7 percent
      Kernel                     4 percent
      Idle                      89 percent
    Model                          RE-J6350-3400
    Serial ID                      NM1742
    Start time                     2008-04-29 16:56:46 UTC
    Uptime                         2 minutes, 20 seconds
    Load averages:                 1 minute   5 minute  15 minute
                                       0.08       0.07       0.03

user@host> show snmp mib walk jnxOperatingCPU   
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 0
jnxOperatingCPU. = 4  < represents the routing-engine if stand alone or node0 if in cluster mode
jnxOperatingCPU. = 0  < represents the routing-engine of node1, if in cluster mode

user@host> show snmp mib get .
jnxOperatingCPU. = 4

In addition to the Routing Engine utilization, there is also the Forwarding Engine utilization. This value is more important in terms of actual traffic-affecting CPU utilization. For forwarding, use the show chassis forwarding command. This command is equivalent to the jnxFwddProcess SNMP MIB object. The most important of these within the jnxFwddProcess hierarchy are the real-time threads (OID .

For example:

user@host> show chassis forwarding             

FWDD status:
  State                                 Online   
  Microkernel CPU utilization         0 percent 
  Real-time threads CPU utilization  12 percent 
  Heap utilization                   23 percent
  Buffer utilization                  5 percent
  Uptime:                             3 minutes, 5 seconds

user@host> show snmp mib walk jnxFwddProcess   
jnxFwddMicroKernelCPUUsage.0 = 0
jnxFwddRtThreadsCPUUsage.0 = 12
jnxFwddHeapUsage.0 = 23
jnxFwddDmaMemUsage.0 = 5
jnxFwddUpTime.0 = 185

user@host> show snmp mib get .
jnxFwddRtThreadsCPUUsage.0 = 12

For more information, refer to Junos® OS Network Management Configuration Guide - Release 12.1.

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