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:
[edit class-of-service] forwarding-policy { next-hop-map map-name { forwarding-class class-name { next-hop [ next-hop-name ]; lsp-next-hop [ lsp-regular-expression ]; non-lsp-next-hop; discard; } forwarding-class-default { discard; lsp-next-hop [ lsp-regular-expression ]; next-hop [next-hop-name]; non-lsp-next-hop; } } class class-name { classification-override { forwarding-class class-name; } } }
Beginning with
Junos OS Release 17.1R1, QFX10000 Series switches support CoS-based
forwarding. [set class-of-service forwarding-policy class] is not supported on QFX10000 Series switches.
Beginning with Junos
OS Release 17.2, MX routers with MPCs or MS-DPCs, VMX, PTX3000 routers,
PTX5000 routers, and VPTX support configuring CoS-based forwarding
(CBF) for up to 16 forwarding classes. All
other platforms support CBF for up to 8 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.
Enabling enhanced-ip is not necessary on PTX routers to
support 16 forwarding classes for CBF.
[set class-of-service forwarding-policy class] is not supported on QFX10000 Series switches.