In this final part of our blog series on QoS with the PIX/ASA, we examine the remaining two tools that we find on some devices - traffic shaping and traffic policing. Read More
This blog is focusing on QoS on the PIX/ASA and is based on 7.2 code to be consistent with the CCIE Security Lab Exam as of the date of this post. I will create a later blog regarding new features to 8.X code for all of you non-exam biased readers :-) 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
This may seem to be a basic topic, but it looks like many people are still confused by the difference between those two concepts. Let us clear this confusion at once! Read More
The goal of this article is to discuss how would the following configuration work in the 3560 series switches: interface FastEthernet0/13 switchport mode access load-interval 30 speed 10 srr-queue bandwidth shape 50 0 0 0 srr-queue bandwidth share 33 33 33 1 srr-queue bandwidth limit 20 Before we begin, let’s recap what we know so far about the 3560 egress queuing: 1) When SRR scheduler is configured in shared mode, bandwidth allocated to each queue is based on relative weight. E.g. when... 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
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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