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Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 3 QoS in an AVVID-Enabled Campus Network
Selecting an Access-Layer Switch
Cos-queue map:
cos-qid
0 - 1
1 - 1
2 - 2
3 - 2
4 - 3
5 - 4
6 - 4
7 - 4
Example 3-15 Displaying Policy Information
3550G-Access#show policy-map interface g 0/2
service-policy input: ACCESS-C3550-LAN-EDGE-IN
class-map: VOICE-CONTROL (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
match: access-group name VOICE-CONTROL
class-map: VOICE (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
match: access-group name VOICE
class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
match: any
0 packets, 0 bytes
5 minute rate 0 bps
Catalyst 2950 as an Access-Layer Switch
The 2950 family of Catalyst switches support enhanced QoS features that can be used in the access layer.
Of particular interest is the ability to classify and mark traffic on ingress to the network via ACLs and
policies. While not as advanced as the Catalyst 4000 Supervisor III or Catalyst 3550 in its flexibility to
identify traffic flows at Layer 3 and Layer 4 via ACLs, the Catalyst 2950 family of switches are Layer
3 aware, making them very powerful. It should be noted that ACLs used to identify traffic in the
Catalyst 2950 are limited to a single TCP or UDP port per Access Control Entry (ACE). Use of the range,
greater than, or less than, keywords is not supported when defining an ACL on the Catalyst 2950. This
can make identification of applications that use a wide range of ports difficult. This means that long
ACLs are required, which may exceed the Catalyst 2950's ACL memory capacity.
The Catalyst 2950 is a very powerful QoS-capable switch for the access layer. However, it does not
support the full set of features required for an IP telephony deployment. The Catalyst 2950 IOS software
provides full support for IP telephony. There is not, however, a Catalyst 2950 hardware option that
provides inline power. This can be designed around through the use of the AC power brick or an inline
power patch panel.
Figure 3-12
shows a general model for the Catalyst 2950 as an access device (as illustrated in the QoS
configurations discussed in this chapter).