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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Standard QoS Configuration Examples
Figure 29-5 QoS Configuration Example Network
QoS Configuration for the Existing Wiring Closet
Figure 29-5 shows an existing wiring closet with Catalyst 2900 XL and 3500 XL switches, for example.
These switches are running Cisco IOS Release 12.0(5)XP or later, which supports the QoS-based
IEEE 802.1p CoS values. QoS classifies frames by assigning priority-indexed CoS values to them and
gives preference to higher-priority traffic.
Recall that on the Catalyst 2900 and 3500 XL switches, you can classify untagged (native) Ethernet
frames at the ingress ports by setting a default CoS priority (switchport priority default
default-priority-id interface configuration command) for each port. For IEEE 802.1Q frames with tag
information, the priority value from the header frame is used. On the Catalyst 3524-PWR XL and 3548
XL switches, you can override this priority with the default value by using the switchport priority
default override interface configuration command. For Catalyst 2950 and Catalyst 2900 XL switches
and other 3500 XL models that do not have the override feature, the Catalyst 3550-12T switch at the
distribution layer can override the IEEE 802.1p CoS value by using the mls qos cos override interface
configuration command.
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