Cisco Catalyst 3550 Series, Software Configuration Manual, Page: 612 / 992

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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Configuring Standard QoS
The default port CoS value is 0.
The default port trust state on all ports is untrusted.
No policy maps are configured.
No policers are configured.
The default CoS-to-DSCP map is shown in Table 29-6 on page 29-52 .
The default IP-precedence-to-DSCP map is shown in Table 29-7 on page 29-52 .
The default DSCP-to-CoS map is shown in Table 29-8 on page 29-54 .
The default DSCP-to-DSCP-mutation map is a null map, which maps an incoming DSCP value to the
same DSCP value.
The default policed-DSCP map is a null map, which maps an incoming DSCP value to the same DSCP
value (no markdown).
The default DSCP-to-switch-priority map maps DSCPs 0 to 15 to priority 0, DSCPs 16 to 31 to
priority 1, DSCPs 32 to 47 to priority 2, and DSCPs 48 to 63 to priority 3.
Standard QoS Configuration Guidelines
Before beginning the QoS configuration, you should be aware of this information:
•
You must disable the IEEE 802.3X flowcontrol on all ports before enabling QoS on the switch. To
disable it, use the flowcontrol receive off and flowcontrol send off interface configuration
commands.
• If you have EtherChannel ports configured on your switch, you must configure QoS classification,
policing, mapping, and queueing on the individual physical ports that comprise the EtherChannel.
You must decide whether the QoS configuration should match on all ports in the EtherChannel.
•
You can classify traffic on an ingress physical port or on a per-ingress-port per-VLAN basis. You
cannot classify traffic at the switch virtual interface level.
Table 29-5 Default Standard QoS Configuration when QoS is Enabled
Port
Type QoS
State
Egress traffic
(DSCP and CoS
Value)
Queue
Queue
Weights Tail-drop
Thresholds CoS Mapping
to Queue
Gigabit-capable
Ethernet ports Enabled
(no
policing)
DSCP=0
CoS=0
(0 means
best-effort
delivery.)
Four queues are
available (no
expedite queue). Each queue has
the same weight. 100%, 100%
WRED is
disabled.
0, 1: queue 1
2, 3: queue 2
4, 5: queue 3
6, 7: queue 4
10/100 Ethernet
ports Enabled
(no
policing)
DSCP=0
CoS=0
(0 means
best-effort
delivery.)
Each of the eight
minimum-reserve
levels have a buffer
size of 100 packets.
The queue selects
the level. Each queue has
the same weight. – 0, 1: queue 1
2, 3: queue 2
4, 5: queue 3
6, 7: queue 4