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Ask The Expert:QoS on Catalyst Switches

Community Manager
Community Manager

Read the bioWith Shashank Singh

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to get an update on QoS on Catalyst 2960, 3550, 3560, 3750, 4500 and 6500 series switches with Cisco expert Shashank Singh. Shashank graduated in 2009 with a bachelor's degree in Computer Science and Engineering from VIT University, Vellore India. Prior to joining Cisco he worked at General Electric as a software engineer. Later on he joined the Cisco Technical Assistance Center as an engineer in October of 2009. He has been working on LAN Switching technologies in TAC since then. Shashank also holds a CCNP certificate. QoS on Catalyst switches is one of the areas of his interest.

Remember to use the rating system to let Shashank know if you have received an adequate response.

Shashank might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Network InfrastructureLAN Switching discussion forum shortly after the event. This event lasts through August 26 , 2011. Visit this forum often to view responses to your questions and the questions of other community members.

73 Replies 73


Thanks for this timely Ask The Expert topic. I am primarily a route/switch engineer that has always skirted around the topic of QoS. I am seeing the obvious holes in my skill-set and am attempting to add this as an area of serious study. My company tends to work primarily with the ISR G1 and G2 routers, and fixed-configuration switches(mostly the 2960 and 3560 series). I have a Ccnp background that includes ONT training. Other than the ONT self-study material and the ONT official course material, what books, classes, or online documents do you suggest for foundational study in QoS for both IOS-based routers and switches?


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Router QoS is pretty generic and there is a lot of quality learning material available on Cisco website in form of documents. Among books, Cisco QoS Exam Certification Guide by Wendell Odom is a good resource. If you are interested in learning the design and implementation aspects, End-to-End QoS Network Design: Quality of Service in LANs, WANs, and VPNs By Tim Szigeti, Christina Hatting makes a good reading.

Though the underlying theory remains the same, understanding and configuring QoS on switches requires a certain degree of platform knowledge. This is mainly because Switches are designed to perform QoS in hardware (ASICs) unlike most of the Routers which depend on the IOS for the same. For example, on Catalyst 6500 switches, QoS is performed by the PFC (Policy Feature Card) on the supervisor engine and  hence it is important to have a prior understanding of what PFC is and how it works.

The best resource for understanding QoS on switches are the platform QoS configuration and troubleshooting documents available on Again as each switch platform implements QoS in a different way, there are separate documents available for each platform. These documents provide a comprehensive perspective of QoS configuration and troubleshooting on respective switch platforms.

Apart from ONT, Cisco offers 642-642 QOS exam which is one of the four qualifying papers in the CCIP (Cisco Certified Internetwork Professional) track. This paper covers Router QoS in detail and also  has a few topics on switch QoS.

You can review the exam topics and official learning resources at

Hope this answers your queries. Feel free to put forward any more questions that you may have.