Cisco Catalyst 3750 - Page 524

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Catalyst 3750 Metro Switch Software Configuration Guide
78-15870-01
Chapter 26 Configuring QoS
Configuring Standard QoS
Step 3
mls qos trust [cos | dscp | ip-precedence] Configure the port trust state.
By default, the port is not trusted. If no keyword is specified, the
default is dscp.
For 802.1Q tunnels, the switch processes inbound traffic on a
standard port according to the trusted setting applied to this port. The
switch configures the inner and outer tags for packets sent over the
ES trunk port.
The keywords have these meanings:
• cos—Classifies an ingress packet by using the packet CoS value.
For an untagged packet, the port default CoS value is used. The
default port CoS value is 0.
For 802.1Q tunnels, the switch copies the inner CoS value to the
outer CoS value and sends the packet out an ES port.
• dscp—Classifies an ingress packet by using the packet DSCP
value if the packet is an IP packet. For a non-IP packet, the
packet CoS value is used if the packet is tagged; for an untagged
packet, the default port CoS is used. Internally, the switch maps
the CoS value to a DSCP value by using the CoS-to-DSCP map.
For 802.1Q tunnels, for a non-IP packet that is untagged, the
switch configures the outer CoS value from the DSCP-to-CoS
map, does not modify the inner CoS value, and sends the packet
out an ES port. For an IP packet, the switch modifies the DSCP
value in the packet if there is a DSCP-to-DSCP mutation map
configured on the standard port. The switch uses the mutated
DSCP value to configure the outer CoS value from the
DSCP-to-CoS map and sends the packet out an ES port
• ip-precedence—Classifies an ingress packet by using the packet
IP-precedence value. For a non-IP packet, the packet CoS value
is used if the packet is tagged; for an untagged packet, the default
port CoS is used. Internally, the switch maps the CoS value to a
DSCP value through the CoS-to-DSCP map.
For 802.1Q tunnels, the switch converts the generated DSCP
value from the DSCP-to-CoS map and uses it as the outer CoS
value in the packet. The switch does not modify the inner CoS
value in the packet and sends the packet out an ES port.
Note When port trust policies are used with 802.1Q tunneling, all
ports sharing the same tunnel VLAN must be configured
with the same trust policy, and the ports involved must use
the same DSCP-to-DSCP mutation map. For more
information, see the “Configuring the
DSCP-to-DSCP-Mutation Map” section on page 26-63.
Step 4
end Return to privileged EXEC mode.
Step 5
show mls qos interface Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose