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Monitoring Interfaces

The below topics discuss the monitoring of the status and traffic, system process information, system properties, statistics for a fast Ethernet and the tracing operations of the interface process.

Monitoring Interface Status and Traffic


View interface status to monitor interface bandwidth utilization and traffic statistics.


  • To view interface status for all the interfaces, enter show interfaces xe.

  • To view status and statistics for a specific interface, enter show interfaces xe interface-name.

  • To view status and traffic statistics for all interfaces, enter either show interfaces xe detail or show interfaces xe extensive.


For details about output from the CLI commands, see show interfaces xe.

Monitoring System Process Information


View the processes running on the device.


To view the software processes running on the device:

user@switch> show system processes


Table 1 summarizes the output fields in the system process information display.

The display includes the total CPU load and total memory utilization.

Table 1: Summary of System Process Information Output Fields




Identifier of the process.


Owner of the process.


Current state of the process.

CPU Load

Percentage of the CPU that is being used by the process.

Memory Utilization

Amount of memory that is being used by the process.

Start Time

Time of day when the process started.

Monitoring System Properties


View system properties such as the name, IP address, and resource usage.


To monitor system properties in the CLI, enter the following commands:

  • show system uptime

  • show system users

  • show system storage


Table 2 summarizes key output fields in the system properties display.

Table 2: Summary of Key System Properties Output Fields



Additional Information

General Information

Serial Number

Serial number of device.


Junos OS Version

Version of Junos OS active on the switch, including whether the software is for domestic or export use.

Export software is for use outside the USA and Canada.


Name of the device.


IP Address

IP address of the device.


Loopback Address

Loopback address.


Domain Name Server

Address of the domain name server.


Time Zone

Time zone on the device.


Current Time

Current system time, in Coordinated Universal Time (UTC).


System Booted Time

Date and time when the device was last booted and how long it has been running.


Protocol Started Time

Date and time when the protocols were last started and how long they have been running.


Last Configured Time

Date and time when a configuration was last committed. This field also shows the name of the user who issued the last commit command.


Load Average

CPU load average for 1, 5, and 15 minutes.

Storage Media

Internal Flash Memory

Usage details of internal flash memory.


External Flash Memory

Usage details of external USB flash memory.

Logged in Users Details


Username of any user logged in to the switch.



Terminal through which the user is logged in.



System from which the user has logged in. A hyphen indicates that the user is logged in through the console.


Login Time

Time when the user logged in.

This is the user@switch field in show system users command output.

Idle Time

How long the user has been idle.


Monitor Statistics for a Fast Ethernet or Gigabit Ethernet Interface


To monitor statistics for a Fast Ethernet or Gigabit Ethernet interface, use the following Junos OS CLI operational mode command:



We recommend that you use the monitor interface fe-fpc/pic/port or monitor interface ge-fpc/pic/port command only for diagnostic purposes. Do not leave these commands on during normal router operations because real-time monitoring of traffic consumes additional CPU and memory resources.

Sample Output

The following sample output is for a Fast Ethernet interface:


Use the information from this command to help narrow down possible causes of an interface problem.


If you are accessing the router from the console connection, make sure you set the CLI terminal type using the set cli terminal command.

The statistics in the second column are the cumulative statistics since the last time they were cleared using the clear interfaces statistics interface-name command. The statistics in the third column are the cumulative statistics since the monitor interface interface-name command was executed.

If the input errors are increasing, verify the following:

  1. Check the cabling to the router and have the carrier verify the integrity of the line. To verify the integrity of the cabling, make sure that you have the correct cables for the interface port. Make sure you have single-mode fiber cable for a single-mode interface and multimode fiber cable for a multimode interface.

  2. For a fiber-optic connection, measure the received light level at the receiver end and make sure that it is within the receiver specification of the Ethernet interface. See Fiber-Optic Ethernet Interface Specifications for the fiber-optic Ethernet interface specifications.

  3. Measure the transmit light level on the Tx port to verify that it is within specification. See Fiber-Optic Ethernet Interface Specificationsfor the optical specifications.

Trace Operations of the Interface Process

To trace the operations of the router or switch interface process, dcd, perform the following steps:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:
  2. Configure the traceoptions statement.
  3. Configure the no-remote-trace option to disable remote tracing.
  4. Configure the file filename option.
  5. Configure the files number option, match regular-expression option, size size option, and world-readable | no-world-readable option.
  6. Configure the tracing flag.
  7. Configure the disable option in flag flag-option statement to disable the tracing operation. You can use this option to disable a single operation when you have defined a broad group of tracing operations, such as all.

You can specify the following flags in the interfaces traceoptions statement:

  • all—Enable all configuration logging.

  • change-events—Log changes that produce configuration events.

  • gres-events—Log the events related to GRES.

  • resource-usage—Log the resource usage for different states.

  • config-states—Log the configuration state machine changes.

  • kernel—Log configuration IPC messages to kernel.

  • kernel-detail—Log details of configuration messages to kernel.

  • select-events—Log the events on select state machine.

By default, interface process operations are placed in the file named dcd and three 1-MB files of tracing information are maintained.

For general information about tracing, see the tracing and logging information in the Junos OS Administration Library for Routing Devices.