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Quality of Service on Catalyst 4500/4000 Switches
Running CatOS FAQ
Document ID: 17953
Questions
Introduction
Which QoS features do Catalyst 4500/4000 switches that run CatOS support?
What is the minimum software that is necessary for QoS on Catalyst 4500/4000 switches
that run CatOS?
Do the Catalyst 4500/4000 switches that run CatOS support rate−limiting or policing on
ports or VLANs?
Can the Catalyst 4500/4000 switches that run CatOS mark or rewrite IP precedence
Type of Service (ToS) bits in an IP packet?
What kind of input scheduling do the Catalyst 4500/4000 switches that run CatOS
provide?
Can the Catalyst 4500/4000 switches that run CatOS change the incoming Class of
Service (CoS) value in IEEE 802.1Q (dot1q) tags?
My server cannot tag Class of Service (CoS) values. Can the Catalyst 4500/4000 switches
that run CatOS tag the traffic from the server for a specific CoS value?
Do the Catalyst 4500/4000 switches that run CatOS honor the incoming Class of Service
(CoS) value in IEEE 802.1Q (dot1q) tags from my IP phones?
Can the Catalyst 4500/4000 switches that run CatOS extend the trust or override the
incoming Class of Service (CoS) value of devices connected to the IP phones?
What kind of output scheduling do the Catalyst 4500/4000 switches that run CatOS
provide?
I enabled QoS on a Catalyst 4500/4000 switch that runs CatOS and now I see
performance issues. What is wrong?
How do the QoS features on the Catalyst 4500/4000 switches that run CatOS compare to
Catalyst 4500/4000 switches that run Cisco IOS Software? How do the features compare
with the features of the Layer 3 (L3) switching module?
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Related Information
Introduction
This document addresses frequently asked questions (FAQ) on the Quality of Service (QoS) feature of the
Cisco Catalyst 4500/4000 (Supervisor Engine I and Supervisor Engine II) series, Catalyst 2948G, Catalyst
2980G, and Catalyst 4912G switches that run Catalyst OS (CatOS). This document refers to these switches as
"Catalyst 4000 switches that run CatOS". For QoS features on Catalyst 4500/4000 switches that run Cisco
IOS® Software, refer to the document Configuring QoS.
For more information on document conventions, refer to the Cisco Technical Tips Conventions.
Q. Which QoS features do Catalyst 4500/4000 switches that run CatOS
support?
A. Catalyst 4500/4000 switches that run CatOS support input classification and output
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Related Manuals for Cisco Catalyst 2820
Summary of Contents for Cisco Catalyst 2820
- Page 1 2980G, and Catalyst 4912G switches that run Catalyst OS (CatOS). This document refers to these switches as "Catalyst 4000 switches that run CatOS". For QoS features on Catalyst 4500/4000 switches that run Cisco IOS® Software, refer to the document Configuring QoS.
- Page 2 Refer to the Installation and Configuration Note for the Catalyst 4000 Layer 3 Services Module for additional information. Policing is supported on the Catalyst 4500/4000 switches that run Cisco IOS Software. For more information, refer to the document QOS Policing and Marking with Catalyst 4000/4500 IOS−Based Supervisor Engines.
- Page 3 A. Yes, but remember that the default CoS for untagged packets is switch−wide and not on a per−port basis. So, all untagged packets are marked the same CoS value. Catalyst 4500/4000 switches that run Cisco IOS Software do support tagging on a per−port basis. For more information, refer to Understanding and Configuring QoS.
- Page 4 Q. How do the QoS features on the Catalyst 4500/4000 switches that run CatOS compare to Catalyst 4500/4000 switches that run Cisco IOS Software? How do the features compare with the features of the Layer 3 (L3) switching module? A.
- Page 5 (egress) rate−limit output command Input/output policer definition with L3 and No, applies to all headers IP and non−IP traffic per port Yes, as of Cisco IOS Software Output Release shaping 12.0(10)W5(18e) with the traffic−shape rate command Classification with an IP...
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Page 6: Related Information
MQC = Modular QoS command−line interface (CLI) 2Q1T = 2 Queues, 1 Threshold CoS = Class of Service 4Q = 4 Queues The Supervisor Engine provides nonblocking switch architecture to obviate the need for input queuing. WRR = weighted round−robin DBL = Dynamic Buffer Limiting Be aware of Cisco bug ID CSCdz48041 exhaustion of tags for policers when configuring policers on many interfaces. - Page 7 Contacts & Feedback | Help | Site Map © 2007 − 2008 Cisco Systems, Inc. All rights reserved. Terms & Conditions | Privacy Statement | Cookie Policy | Trademarks of Cisco Systems, Inc. Updated: Nov 16, 2007 Document ID: 17953...