In this first of a series of blog posts regarding Catalyst QoS, we will exam the AutoQoS capabilities on the 3560 Catalyst devices. AutoQoS allows for the automation of QoS settings for the switch with an absolute minimum of configuration required from the engineer. In particular, the 3560 AutoQoS features automates the classification and congestion management configurations required in VoIP environments. You should note that the 3560 AutoQoS has much “catching up” to do when you compare this... Read More
People are often confused with per-VLAN classification, policing and marking features in the Catalyst 3550 and 3560 models. The biggest problem is lack of comprehensive examples in the Documentation CD. Let's quickly review and compare traffic policing features available on both platforms. The material below is a condensed excerpt of several Catalyst QoS topics covered in the “QoS” section of our IEWB VOL1 V5. You will find more in-depth explanations and large number of simulation-based... Read More
I found it important to make a small post in reply to the following question: Read More
The 3560 QoS processing model is tightly coupled with it’s hardware architecture borrowed from the 3750 series switches. The most notable feature is the internal switch ring, which is used for the switch stacking purpose. Packets entering a 3560/3750 switch are queued and serviced twice: first on the ingress, before they are put on the internal ring, and second on the egress port, where they have been delivered by the internal ring switching. In short, the process looks as follows:... Read More
Catalyst QoS configuration for IP Telephony endpoints is one of the CCIE Voice labs topics. Many people have issues with that one, because of need to memorize a lot of SRND recommendations to do it right. The good news is that during the lab exam you have full access to the QoS SRND documents and UniverCD content. The bad news is that you won’t probably have enough time to navigate the UniverCD with comfort plus the reference configurations often have a lot of typos and mistakes in them. Read More
QoS features available on Catalyst switch platforms have specific limitations, dictated by the hardware design of modern L3 switches, which is heavily optimized to handle packets at very high rates. Catalyst switch QoS is implemented using TCAM (Ternary Content Addressable Tables) - fast hardware lookup tables - to store all QoS configurations and settings. We start out Catalyst QoS overview with the old, long time available in the CCIE lab, the Catalyst 3550 model. Read More

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