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[EX] EX Series switches software processes overview



Article ID: KB11188 KB Last Updated: 09 Sep 2020Version: 5.0

The JUNOS software running on the Routing Engine and Packet Forwarding Engine consists of multiple processes that are responsible for individual functions. The separation of functions provides operational stability, because each process accesses its own protected memory space. In addition, because each process is a separate software package, you can selectively upgrade all or part of the JUNOS software, for added flexibility.

This article describes the main software processes that are running on EX Series switching platforms.



The EX Series switches software has the following main processes for the different functions on the switch. Each process, also known as a daemon, runs as an independent software module.

chassisd - The chassis process

The chassisd process controls the chassis and its components as follows:

  • Detects hardware on the system that is used to configure network interfaces

  • Monitors the physical status of hardware components and field-replaceable units (FRUs), detecting when environment sensors such as temperature sensors are triggered

  • Relays signals and interrupts—for example, when devices are taken offline, so that the system can close sessions and shut down gracefully

dcd - Interface process, also called device control process

The dcd process configures and monitors network interfaces by defining physical characteristics such as link encapsulation, hold times, and keepalive timers.

fwdd - Forwarding process

The fwdd process is responsible for most of the packet transmission through a routing platform. The overall performance of a device is largely determined by the effectiveness of the forwarding process.

mgd - Management process

The mgd process manages the system as follows:

  • Provides communication between the other processes and an interface to the configuration database

  • Populates the configuration database with configuration information and retrieves the information when queried by other processes to ensure that the system operates as configured

  • Interacts with the other processes when commands are issued through one of the user interfaces on the router

rpd - Routing protocol process

The rpd process defines how routing protocols such as RIP, OSPF, and BGP operate on the device, including selecting routes and maintaining forwarding tables. 

  • To monitor system process, use the command show system processes. For example, to monitor the mgd process:

user@switch> show system processes |grep mgd   

   515  ??  I      0:00.94 /usr/sbin/mgd -N
  1216  ??  Is     0:00.33 mgd: (mgd) (lab)/dev/ttyp1 (mgd)
  2773  ??  Ss     0:00.04 mgd: (mgd) (lab)/dev/ttyp2 (mgd)

In this example, the management process is running through the command /usr/sbin/mgd -N with process number 515.


Modification History:

2020-09-09: Article reviewed for accuracy; reference links added and no other changes made; article found to be relevant and valid


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