We have Juniper SRX3600 running in our network. At the moment only 2 x PEM Modules (AC Power Supply) are installed in the chassis while other 2 x PEM are not. This is shown below from the output of 'show chassis environment'.

user@SRX3600> show chassis environment 
Class Item                           Status     Measurement
Temp  PEM 0                          OK         24 degrees C / 75 degrees F
      PEM 1                          OK         24 degrees C / 75 degrees F
      PEM 2                          Absent    
      PEM 3                          Absent  

However when 1 x PEM Module goes down due to issue in input power supply , then all line cards (FPC / SPC) are down except Routine Engine (observed by the output of 'show chassis routing-engine').

It is clear that both PEM 0 and PEM 1 are required for normal working of SRX3600. If we want to introduce PEM 2 and PEM 3 into the chassis , then how will be the redundancy work i.e. which PEM modules will be backup of each other when there are 4 x PEMs installed?

We do have multiple input sources of power supplies in the data supplies. Hence is it possible to provide input power to 2 x PEMs (which are backup of each other , I dont know which PEMs) from one source and remaining 2 x PEMs getting power from the other source?

In this way , there will be redundancy not only from PEMs perspective but also from input power supply source.

Just for information

This level of redundancy is currently working for Juniper MX960s in data center which have 4 x PEMs installed with 2 x PEMs getting power from one source while other 2 x PEMs getting power from other source.

Many Thanks

1 Answer 1


You probably need one or two more PEMs. This Juniper document is a good planning resource for SRX3600 power budgeting.

All the PEMs in the SRX3600 load-share so the problem isn't which slots are occupied by PEMs but rather the total available power supply. There are no zones or similar complications like there are in some other Juniper chassis.

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