Enterprise QoS Solution Reference Network Design Guide

Chapter 2 Campus QoS Design
Figure 2-19 Access Layer Catalyst 4500 QoS Design Options
Enable QoS
Globally
Version 3.3
Trusted-Endpoint
Model
AutoQoS–VoIP
Model
PC + SoftPhone +
Scavenger Model
Untrusted Server +
Scavenger Model
IP Phone + PC +
Scavenger (Basic) Model
IP Phone + PC +
Scavenger (Adv) Model
Access-Edges
Figure 2-20 Distribution and/or Core Layer Catalyst 4500 QoS Design
Enable QoS
Globally
Trust-DSCP
1P3Q1T
Queuing + DBL
1P3Q1T
Queuing + DBL
1P3Q1T
Queuing + DBL
1P3Q1T
Queuing + DBL
1P3Q1T
Queuing + DBL
1P3Q1T
Queuing + DBL
Catalyst 4500 Supervisor II+/III/IV/V—QoS Considerations and Design
Interswitch Links
1P3Q3T
Queuing + WTD
Trust-DSCP
Uplinks to
Distribution Layer
Note To narrow the scope of our discussion to the most current and relevant versions of the Catalyst 4500
switch family, only the Catalyst 4500 with Supervisors II+, III, IV and V are examined in this design
chapter. For discussions of older versions of Catalyst 4000/4500s, refer to the Cisco Press book, Cisco
Catalyst QoS: Quality of Service in Campus Networks, by Mike Flannagan, Richard Froom, and Kevin
Turek.
Much of the Catalyst MLS QoS syntax is supported on the Catalyst 4500; however, the mls prefix
keyword is usually omitted from the configuration commands. For example, as with the Catalyst 3550
and 2970/3560/3750, QoS is globally disabled on the Catalyst 4500 by default. However, the command
to enable QoS globally on a Catalyst 4500 is simply qos, not mls qos.
The verification commands are issued in the same manner, with the mls keyword omitted. Generally
speaking, show mls qos [...] verification commands from other Catalyst platforms are translated to show
qos [...] verification commands on the Catalyst 4500 platforms.
While QoS is globally disabled on the Catalyst 4500, all frames/packets are passed-through the switch
unaltered (which is equivalent to a trust CoS and trust DSCP state on all ports). When QoS is globally
enabled, however, then all DSCP and CoS values are (by default) set to 0 (which is equivalent to an
untrusted state on all ports).
The verification command to check whether QoS has been globally enabled on the Catalyst 4500, along
with the configuration command, are shown below.
Enterprise QoS Solution Reference Network Design Guide
1P3Q1T Queuing +
DBL
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