User Guide

31-11
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 31 Configuring PFC QoS
Understanding How PFC QoS Works
PFC QoS Feature Summary
These sections summarize the PFC QoS features:
• Ingress LAN Port Features, page 31-11
• Ingress OSM Port Features, page 31-11
• PFC QoS Features, page 31-11
• Egress LAN Port Features, page 31-12
• Egress OSM Port Features, page 31-12
• MSFC Features, page 31-12
Ingress LAN Port Features
PFC QoS supports classification, marking, scheduling, and congestion avoidance using Layer 2 CoS
values at ingress LAN ports. Classification, marking, scheduling, and congestion avoidance at ingress
LAN ports do not use or set Layer 3 IP precedence or DSCP values. You can configure ingress LAN port
trust states that can be used by the PFC to set Layer 3 IP precedence or DSCP values and the Layer 2
CoS value. See Figure 31-3 and the “Ingress LAN Port Features” section on page 31-12.
Ingress OSM Port Features
PFC QoS associates CoS zero with all traffic received through ingress OSM ports. You can configure
ingress OSM port trust states that can be used by the PFC to set Layer 3 IP precedence or DSCP values
and the Layer 2 CoS value. You can configure the trust state of each ingress OSM port as follows:
• Untrusted (default)
• Trust IP precedence
• Trust DSCP
• Trust CoS (CoS is always zero because the default port CoS is not configurable on OSM ports.)
PFC QoS Features
On the PFC, PFC QoS supports ingress classification, marking, and policing using policy maps. You can
attach one policy map to an ingress port. Each policy map can contain multiple policy-map classes. You
can configure a separate policy-map class for each type of traffic received through the ingress port. See
the “PFC Marking and Policing” section on page 31-16.
Note • You can globally disable marking and policing with the mls qos queueing-only command (see the
Enabling Queueing-Only Mode, page 31-34).
• You can disable marking and policing on a per-interface basis with the no mls qos interface
command (see the “Enabling or Disabling PFC Features on an Interface” section on page 31-51.