Cisco Systems EA6500 Manual De Usuario

For all egress traffic, PFC QoS uses a configurable mapping table to derive a CoS value from the internal 
DSCP value associated with traffic (see the 

). PFC QoS sends the CoS value to the egress LAN ports for use in scheduling and 

to be written into ISL and 802.1Q frames.

You can globally disable marking and policing with the mls qos queueing-only command (see the 

You can disable marking and policing on a per-interface basis with the no mls qos interface 
command (see the 

.

The PFC supports filtering, marking, and policing using policy maps (see the 

). Each policy map can contain multiple policy-map classes. You can 

configure a separate policy-map class for each type of received traffic.

Policy-map classes specify filtering with the following:

Cisco IOS access control lists (optional for IP, required for IPX and MAC-Layer filtering)

Class-map match commands for Layer 3 IP precedence and DSCP values

Policy-map classes specify actions with the following:

(Optional) Policy-map class trust commands. If specified, PFC QoS applies the policy-map class 
trust state to matched traffic. Policy-map class trust states supersede ingress LAN port trust states.

If traffic matches a policy-map class that does not contain a trust command, the trust state 
remains as set on the ingress LAN port.

(Optional) Aggregate and microflow policers, which can use bandwidth limits to either mark or drop 
both conforming and nonconforming traffic. See the 

The PFC uses the trust state (set by the ingress LAN port configuration or by a trust policy-map class 
command) to select the Layer 2 and Layer 3 PFC QoS labels that the egress port writes into the packets 
and frames before it is transmitted:

Trust IP precedence—Sets the internal DSCP value to a mapped value based on received IP 
precedence (see the 

Trust DSCP—Sets the internal DSCP value to the received DSCP value.

Trust CoS—Sets the internal DSCP value to a mapped value based on received or port CoS. With trust 
CoS, note the following:

Received CoS is overwritten with port CoS in traffic received through ports not configured to 
trust CoS.

Received CoS is preserved only in traffic received through ports configured to trust CoS.

Port CoS is applied to all traffic received in untagged frames, regardless of the port trust state.

For information about mapping, see the