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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Standard QoS Configuration Examples
Figure 29-11 QoS Configuration Example Network
QoS Configuration for the Existing Wiring Closet
The existing wiring closet in Figure 29-11 consists of Catalyst 3500 XL and 2900 XL switches. 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 3500 XL and 2900 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 ISL or 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 3500 XL, 2950, other 2900
XL models that do not have the override feature, the Catalyst 3550-12T switch at the distribution layer
can override the 802.1P CoS value by using the mls qos cos override interface configuration command.
Cisco router
Existing wiring closet
Catalyst 2900 and 3500 XL
switches
Intelligent wiring closet
Catalyst 3550 switches
To Internet
Catalyst 3550-12G switch
Gigabit Ethernet 0/5
Gigabit Ethernet 0/2
Gigabit
Ethernet
0/2
Gigabit
Ethernet
0/1
Trunk
link
Gigabit Ethernet 0/1
Trunk
link
End
stations
Video server
172.20.10.16
51290
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