Configuring flow on Juniper devices

Provides commands and examples to configure J-Flow on an SRX Series device.

Command modes

Command mode Description
Operational mode
When you log in to the router and type the CLI command, you are automatically in operational mode:
user@host>
 This mode displays the status of the device. In operational mode, you enter commands to monitor and troubleshoot the Junos OS, devices, and network connectivity.
Configuration mode
user@host>configure
user@host#
To exit the mode, give the following commands:
user@host# commit and-quit
commit complete
user@host
To exit without commit:
user@host# exit
Exiting configuration mode
user@host>
 A configuration for a device that is running on Junos OS is stored as a hierarchy of statements. In configuration mode, you enter these statements to define all properties of the Junos OS, including interfaces, general routing information, routing protocols, user access, and several system and hardware properties.

Active Flow monitoring

Flow monitoring versions 5, 8, and 9 support active flow monitoring. For active flow monitoring, the monitoring station participates in the network as an active router. A router performs the following actions during active Flow monitoring:
  • Sampling

    The router selects and analyzes only a portion of the traffic.

  • Sampling with templates

    The router selects, analyzes, and arranges a portion of the traffic into templates.

  • Sampling per sampling instance

    The router selects, analyzes, and arranges a portion of the traffic according to the configuration and binding of a sampling instance.

  • Port mirroring

    The router copies entire packets and sends the copies to another interface.

  • Multiple port mirroring

    The router sends multiple copies of monitored packets to multiple export interfaces with the next-hop-group statement at the (edit forwarding-options) hierarchy level.

  • Discard accounting

    The router accounts for selected traffic before it discards. Such traffic is not forwarded out of the router. Instead, the traffic is quarantined and deleted.

  • Flow-tap processing

    The router processes requests for active flow monitoring dynamically by using the Dynamic Tasking Control Protocol (DTCP).

Some of the commands for these actions are described here.