Cisco NCS 5500 Series Configuration Manual page 65

Implementing MPLS Traffic Engineering
MPLS-TE Features - Details
PBTS Forward Class
A class-map is defined for various types of packets and these class-maps are associated with a forward-class.
A class-map defines the matching criteria for classifying a particular type of traffic and a forward-class defines
the forwarding path these packets should take.
After a class-map is associated with a forwarding-class in the policy map, all the packets that match the
class-map are forwarded as defined in the policy-map. The egress traffic engineering (TE) tunnel interfaces
that the packets should take for each forwarding-class is specified by associating the TE interface explicitly
(or implicitly in case of default value) with the forward-group.
When the TE interfaces are associated with the forward-class, they can be exported to the routing protocol
module using the auto-route command. This will then associate the route in the FIB database with these
tunnels. If the TE interface is not explicitly associated with a forward-class, it gets associated with a default-class
(0). All non-TE interfaces will be routed to the forwarding plane (with forward-class set to default-class) by
the routing protocol.
MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
57