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Configuring the Number of Schedulers per Port for Ethernet IQ2 PICs

You can oversubscribe the Ethernet IQ2 family of PICs. Because of the bursty nature of Ethernet use, traffic received by the PIC can be several orders of magnitude greater than the maximum bandwidth leaving the PIC and entering the router. Several configuration statements apply only to Ethernet IQ2 PICs and allow the PIC to intelligently handle the oversubscribed traffic.


The total of the input guaranteed rates for oversubscribed IQ2 PICs is limited to the FPC or PIC bandwidth.

By default, each Ethernet IQ2 PIC is allocated a fixed number of the 1024 available schedulers for each port during PIC initialization. For example, the 8-port Gigabit Ethernet IQ2 PIC is allocated 128 schedulers for each port. This number cannot be changed after the PIC is operational and can limit the utilization of shapers among the ports. Each of the 1024 schedulers is mapped at the logical interface (unit) level, and each scheduler map can support up to eight forwarding classes.

Schedulers are allocated in multiples of four. Three schedulers are reserved on each port. One is for control traffic, one is for port-level shaping, and the last is for unshaped logical interface traffic. These are allocated internally and automatically. The fourth scheduler is added when VLANs are configured.

When you configure schedulers for a port on an Ethernet IQ2 PIC:

  • The three reserved schedulers are added to the configured value, which yields four schedulers per port.

  • The configured value is adjusted upward to the nearest multiple of 4 (schedulers are allocated in multiples of 4).

  • After all configured schedulers are allocated, any remaining unallocated schedulers are partitioned equally across the other ports.

  • Any remaining schedulers that cannot be allocated meaningfully across the ports are allocated to the last port.

If the configured scheduler number is changed, the Ethernet IQ2 PIC is restarted when the configuration is committed.


If you deactivate and reactivate a port configured with a non-default number of schedulers, then the entire Ethernet IQ2 PIC restarts.

You can configure between 1 and 1024 schedulers on a port.

The following example allocates 100 schedulers to port 1 on an 8-port Gigabit Ethernet IQ2 PIC. The example shows the final scheduler allocation numbers for each port on the PIC. By default, each port would have been allocated 1024 / 8 = 128 schedulers.To configure the number of schedulers assigned to a port on an Ethernet IQ2 PIC:

  • Specify the schedulers statement for the Ethernet IQ2 PIC interface at the [edit interfaces ge-fpc/pic/port] hierarchy level.

This configuration results in the port and scheduler configuration shown in Table 1.

Table 1: Scheduler Allocation for an Ethernet IQ2 PIC

Ethernet IQ2 PIC Port

Number of Allocated Schedulers




104 (100 configured, plus 3 reserved, rounded up to multiple of 4: 100 + 3 +1= 104)












152 (128 plus the 24 remaining that cannot be meaningfully allocated to other ports)