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Forwarding Policy Options Overview

Class-of-service (CoS)-based forwarding (CBF) enables you to control next-hop selection based on a packet’s class of service and, in particular, the value of the IP packet’s precedence bits.

For example, you might want to specify a particular interface or next hop to carry high-priority traffic while all best-effort traffic takes some other path. When a routing protocol discovers equal-cost paths, Junos picks a path at random or load-balance across the paths through either hash selection or round robin. CBF allows path selection based on class.

To configure CBF properties, include the following statements at the [edit class-of-service] hierarchy level:

Platform-Specific CBF Behavior

Use the following table to review platform-specific behaviors for your platforms.

Table 1: Platform-Specific CBF Behavior

Platform

Difference

MX Series

  • MX routers support configuring CBF for up to 16 forwarding classes.

  • To support up to 16 forwarding classes for CBF on MX routers, enable enhanced-ip at the [edit chassis network-services] hierarchy level.

PTX Series

  • PTX routers support configuring CBF for up to 16 forwarding classes.

  • Enabling enhanced-ip is not necessary on PTX routers to support 16 forwarding classes for CBF.