| QoS is a big topic on your BCMSN and CCNP | | | | appropriate distribution layer switches.Any traffic |
| exams, and for good reason. As more and more | | | | received by core switches should already be |
| traffic flows through today's networks, accurately | | | | classified and marked as needed. The key with |
| applying QoS to both your routers and switches | | | | core switches is to use a simple queuing setup to |
| becomes more important.Note the phrase | | | | keep the switching process fast. Fast, fast, |
| "accurately applying". You must have a plan in | | | | fast!Real-world note - Low Latency Queuing (LLQ) |
| place before you start configuring QoS on your | | | | is an excellent choice for core switches. The |
| switches, and to create such a plan you should | | | | name says it all - low latency! The configuration of |
| use Cisco's Three-layer Hierarchical Model.This | | | | LLQ is not a BCMSN topic, but a quick search on |
| model breaks switches down into three main | | | | the term low latency queuing will quickly bring up |
| groups - Access, Distribution, and Core. You're | | | | several Cisco LLQ configuration |
| familiar with these groups from your CCNA | | | | documents.Knowing the three layers of Cisco's |
| studies, and now you've got to apply this | | | | networking model and the basic QoS operation |
| knowledge.The QoS workload should be borne by | | | | and commands is vital to passing the CCNP |
| the Access and Distribution layers, because the | | | | exams, but even more importantly, you've got to |
| Core layer switches need to be left alone as | | | | apply this knowledge carefully and accurately to |
| much as possible to their primary purpose - | | | | make QoS work for you in today's production |
| switching!Traffic should generally be classified and | | | | networks.Chris Bryant, CCIE #12933, is the owner |
| marked at the Access layer. This allows traffic to | | | | of The Bryant Advantage, home of free CCNP |
| be assigned the desired QoS values and carry | | | | and CCNA tutorials, The Ultimate CCNA Study |
| that value throughout the network.If you choose | | | | Package, and Ultimate CCNP Study Packages.You |
| to change CoS-DSCP mappings, this will generally | | | | can also join his RSS feed and visit his blog, which |
| be done at the Distribution layer. Since distribution | | | | is updated several times daily with new Cisco |
| layer switches will be receiving frames and | | | | certification articles, free tutorials, and daily CCNA |
| packets with QoS values from the access layer | | | | CCNP exam questions! Details are on the |
| switches, the appropriate "trust" and "no trust" | | | | website. |
| statements should be configured on the | | | | |