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Chapter 3 QoS in an AVVID-Enabled Campus Network

Selecting a Distribution-Layer Switch

Example 3-17 Displaying the Queuing Mechanism and Queue Assignments

2950-Access#show wrr-queue band

wrr-queue bandwidth is disabled

2950-Access#show wrr-que cos

CoS Value : 0 1 2 3 4 5 6 7

Priority Queue : 1 1 2 2 3 3 4 4

Selecting a Distribution-Layer Switch

There are many choices for distribution-layer Catalyst switches. The most common switch in this layer
of a hierarchical network design is the Catalyst 6500. The Catalyst 6500 series has advanced QoS
features via the PFC that makes it an ideal choice for this location in the network. The Catalyst 4000
with Supervisor III is also well suited for this task. The primary difference between a Catalyst 6500
series and the Catalyst 4000 when used in this part of a network design is scalability. The Catalyst 6500
can scale to 256 Gbps with 10 Gbps interfaces while the Catalyst 4000 with Supervisor III can only scale
to 32 Gbps interfaces. Additionally, for very small networks (where density, scalability, and investment
protection are not a primary concern), the Catalyst 3550 family of switches offers a robust QoS feature
set that makes it a good fit for the distribution layer.

After you configure the access switch and attached it to the distribution layer, you must set up QoS on
the distribution switches. This section illustrates how to do that on the various switches mentioned
earlier in this chapter.

Catalyst 6500 (with Catalyst OS) as a Distribution-Layer Switch

Figure 3-13

shows a general model for the Catalyst 6500 (with Catalyst OS) as a distribution device (as

illustrated in the QoS configurations discussed in this chapter).