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Configuring Up to 16 Forwarding Classes

By default on all platforms, four output queues are mapped to four forwarding classes, as shown in Table 27. For J-series, M320, and T-series platforms, you can configure more than four forwarding classes and queues.

On J-series Services Routers, you can configure up to eight forwarding classes and eight queues with one-to-one mapping of forwarding classes to queues. On the M120, M320, MX-series, and T-series platforms, you can configure up to 16 forwarding classes and eight queues, with multiple forwarding classes assigned to single queues. The concept of assigning multiple forwarding classes to a queue is sometimes referred to as creating forwarding-class aliases. This section discusses the M320 and T-series platform configuration. For information about the J-series platform configuration, see Configuring Up to Eight Forwarding Classes.

Mapping multiple forwarding classes to single queues is useful. Suppose, for example, that forwarding classes are set based on multifield (MF) packet classification, and the MF classifiers are different for core-facing interfaces and customer-facing interfaces. Suppose you need four queues for a core-facing interface and five queues for a customer-facing interface, where fc0 through fc4 correspond to the classifiers for the customer-facing interface, and fc5 through fc8 correspond to classifiers for the core-facing interface, as shown in Figure 7.

Figure 7: Customer-Facing and Core-Facing Forwarding Classes

Image g016702.gif

In this example, there are nine classifiers and, therefore, nine forwarding classes. The forwarding class-to-queue mapping is shown in Table 28.

Table 28: Sample Forwarding Class-to-Queue Mapping

Forwarding Class Names	Queue Number
fc0 fc5	0
fc1 fc6	1
fc2 fc7	2
fc3 fc8	3
fc4	4

To configure up to 16 forwarding classes, include the class and queue-num statements at the [edit class-of-service forwarding-classes] hierarchy level:



[edit class-of-service forwarding-classes]
class class-name queue-num queue-number;

You can configure up 16 different forwarding-class names. The corresponding output queue number can be from 0 through 7. Therefore, you can map multiple forwarding classes to a single queue. If you map multiple forwarding classes to a queue, the multiple forwarding classes must refer to the same scheduler (at the [edit class-of-service scheduler-maps map-name forwarding-class class-name scheduler scheduler-name] hierarchy level).

When you configure up to 16 forwarding classes, you can use them as you can any other forwarding class—in classifiers, schedulers, firewall filters (MF classifiers), policers, CoS-based forwarding, and rewrite rules.

Note: The following limitations apply:

The class and queue statements at [edit class-of-service forwarding-classes] hierarchy level are mutually exclusive. In other words, you can include one or the other of the following configurations, but not both:[edit class-of-service forwarding-classes] queue queue-number class-name; [edit class-of-service forwarding-classes] class class-name queue-num queue-number;
When you configure IEEE 802.1p rewrite marking on Gigabit Ethernet IQ and Gigabit Ethernet IQ2 PICs, you cannot configure more that eight forwarding classes.
For GRE and IP-IP tunnels, IP precedence and DSCP rewrite marking of the inner header do not work with more than eight forwarding classes.
If the ID assigned to a forwarding class is from 8 through 15 and if the incoming interface is on a Gigabit Ethernet IQ2 PIC, fixed classification does not work. Fixed classification works on Gigabit Ethernet IQ2 PICs if the forwarding class used for fixed classification has an ID from 0 through 7.

You can determine the ID number assigned to a forwarding class by issuing the show class-of-service forwarding-class command. You can determine whether the classification is fixed by issuing the show class-of-service forwarding-table classifier mapping command. In the command output, if the Table Type field appears as Fixed, the classification is fixed. For more information about fixed classification, see Assigning a Forwarding Class to an Interface.

For information about configuring eight forwarding classes on ATM2 IQ interfaces, see Enabling Eight Queues on ATM2 IQ Interfaces.

This section discusses the following topics:

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