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[SRX] Data Plane Memory observed in the output of 'show chassis routing-engine' command on SRX Branch Devices



Article ID: KB26490 KB Last Updated: 23 Jul 2020Version: 2.0

This article provides information on how to interpret the output of the chassis routing-engine command and the memory allocated between data plane and control-plane.


Note: This information is applicable only for SRX Branch series devices . 

The command displays the control plane and data plane memory, which represents the RAM that is shared between RE and PFE; of which a certain percentage is pre-allocated for utilization.

The allocation of memory is as per the system design and does not hinder the capacity of the device to route, when it is in production.

Sample output:
user@host> show chassis routing-engine
Routing Engine status:
Temperature 35 degrees C / 95 degrees F
CPU temperature 35 degrees C / 95 degrees F
Total memory 2048 MB Max 1085 MB used ( 53 percent)
Control plane memory 1104 MB Max 386 MB used ( 35 percent)
Data plane memory 944 MB Max 699 MB used ( 74 percent) > memory which is allocated and used respectively.
CPU utilization:
User 3 percent
Background 0 percent
Kernel 1 percent
Interrupt 0 percent
Idle 95 percent
Serial ID AACN2635
Start time 2012-12-08 05:27:46 UTC
Uptime 3 days, 20 hours, 49 minutes, 33 seconds
Last reboot reason 0x200:normal shutdown
Load averages: 1 minute 5 minute 15 minute
0.04 0.05 0.06
  • As per the above output, the Control Plane has the maximum of 1104 MB and Data Plane has the maximum of 944MB that is a total RAM of [1104+944=2048MB]; which is basically 2GB.

  • The Control Plane memory displays 386 MB being used, which is 35 percent of 1104MB and Data Plane Memory displays 699MB being used, which is 74 percent of 944MB.

  • In SRX branch devices, the data core runs in a continuous cycle in a tight loop without interrupts to process a packet as soon as it arrives; so, it may seem that the CPU is always processing, even when no real traffic is passing. If the traffic load increases, the used Data plane memory will also go up. So, a certain amount of memory is allocated from the memory reserve. From the above output, you can see that 74 percent of Data Plane memory is being utilized out of 944MB.

  • So, you can see the amount of memory (74 percent and 35 percent respectively) being allocated for Data Plane and Control Plane from the RAM reserve, which is shared by RE and PFE.
Modification History:
2020-07-18: Article reviewed for accuracy;‚Äč made minor non-technical changes.

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