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Example: Configuring Forwarding Class Sets

A forwarding class set (fc-set) is a priority group for enhanced transmission selection (ETS) traffic control. Each fc-set consists of one or more forwarding classes (priorities). Classifiers map traffic to forwarding classes based on code points, and forwarding classes are mapped to output queues.

ETS enables you to configure link resources (bandwidth and bandwidth sharing characteristics) for an fc-set, and then allocate the fc-set’s resources among the forwarding classes that belong to the fc-set. This is called two-tier, or hierarchical, scheduling. Traffic control profiles control the scheduling for the fc-set (priority group), and schedulers control the scheduling for individual forwarding classes (priorities).

Configuring Forwarding Class Sets

Step-by-Step Procedure

  1. Define the lan-pg priority group (fc-set) and assign to it the forwarding classes best-effort-1 and best-effort-2:

  2. Define the san-pg priority group and assign to it the forwarding classes fcoe and fcoe-2:

  3. Define the hpc-pg priority group and assign to it the forwarding classes nc and high-perf:

  4. Map the three forwarding class sets to an interface (the output traffic control profiles associated with the forwarding class sets determine the class of service scheduling for the priority groups):


This example uses the following hardware and software components:

  • One switch (this example was tested on a Juniper Networks QFX3500 Switch)

  • Junos OS Release 11.1 or later for the QFX Series or Junos OS Release 14.1X53-D20 or later for the OCX Series.


You can configure up to three unicast fc-sets and one multicast fc-set. A common way to configure unicast priority groups is to configure separate fc-sets for local area network (LAN) traffic, storage area network (SAN) traffic, and high-performance computing (HPC) traffic, and then assign the appropriate forwarding classes to each fc-set.


If you configure a strict-high priority forwarding class, you must create an fc-set that is dedicated only to strict-high priority traffic. You can only configure one strict-high priority forwarding class, and only one fc-set can contain a strict-high priority queue. Queues that are not strict-high priority cannot belong to the same fc-set as a strict-high priority queue. The multidestination fc-set cannot contain a strict-high priority queue.

To apply ETS, you use a traffic control profile to map one or more fc-sets to a physical egress port. You can map up to three unicast forwarding class sets and one multidestination forwarding class set to each port. When you map an fc-set to a port, the port uses hierarchical scheduling to allocate port resources to the priority group (fc-set) and to allocate the priority group resources to the queues (forwarding classes) that belong to the priority group.

This example describes how to:

  • Configure three fc-sets called lan-pg, san-pg, and hpc-pg.

  • Assign forwarding classes to each of the fc-sets.

  • Apply the fc-sets and their output traffic control profiles to an egress interface.

This example does not describe how to configure the forwarding classes assigned to the fc-sets or how to configure traffic control profiles (scheduling). Example: Configuring CoS Hierarchical Port Scheduling (ETS) provides a complete example of how to configure ETS, including forwarding class and scheduling configuration. Table 1 shows the configuration components for this example:

Table 1: Components of the Forwarding Class Sets Configuration Example




QFX3500 switch

LAN traffic priority group

Forwarding class set: lan-pg

Forwarding classes: best-effort-1, best-effort-2

SAN traffic priority group

Forwarding class set: san-pg

Forwarding classes: fcoe, fcoe-2


OCX Series switches do not support FCoE traffic or lossless Layer 2 transport. If you were configuring this example on an OCX Series switch, you could omit this priority group, or rename it and map different forwarding classes to it.

HPC traffic priority group

Forwarding class set: hpc-pg

Forwarding classes: nc, high-perf

Egress interface



To verify the priority group configuration, perform these tasks:

Verifying Forwarding Class Set Membership


Verify that you configured the lan-pg, san-pg, and hpc-pg priority groups with the correct forwarding classes.


List the forwarding class set member configuration using the operational mode command show configuration class-of-service forwarding-class-sets:

Verifying the Egress Interface Configuration


Verify that egress interface xe-0/0/7 is associated with the lan-pg, san-pg, and hpc-pg priority groups and with the correct output traffic control profiles.


Display the egress interface using the operational mode command show configuration class-of-service interfaces xe-0/0/7: