Standard Qos Configuration Guidelines - Cisco Catalyst 3550 series Software Configuration Manual

Configuring Standard QoS
Table 29-5 Default Standard QoS Configuration when QoS is Enabled
Port QoS
Type State
Gigabit-capable Enabled
Ethernet ports
(no
policing)
10/100 Ethernet Enabled
ports
(no
policing)
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
The default IP-precedence-to-DSCP map is shown in
The default DSCP-to-CoS map is shown in
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:
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•
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Catalyst 3550 Multilayer Switch Software Configuration Guide
29-26
Egress traffic
(DSCP and CoS
Value)
DSCP=0
CoS=0
(0 means
best-effort
delivery.)
DSCP=0
CoS=0
(0 means
best-effort
delivery.)
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.
Queue
Queue Weights
Four queues are Each queue has
available (no the same weight.
expedite queue).
Each of the eight Each queue has
minimum-reserve the same weight.
levels have a buffer
size of 100 packets.
The queue selects
the level.
Table 29-6 on page
Table 29-7 on page
Table 29-8 on page
Chapter 29 Configuring QoS
Tail-drop CoS Mapping
Thresholds to Queue
100%, 100% 0, 1: queue 1
WRED is 2, 3: queue 2
disabled.
4, 5: queue 3
6, 7: queue 4
– 0, 1: queue 1
2, 3: queue 2
4, 5: queue 3
6, 7: queue 4
29-52.
29-52.
29-54.
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