The choice of switching method is determined by: IOS version Router platform Which features are enabled
With new versions of IOS, Cisco tries to make it possible to switch packets with some faster method than process switching, even if extra processing for some feature is required. In the olden days, for example, access lists meant process switching. Then they figured out how to support access lists with fast switching. When NAT first came out it meant process switching was required. That's not true any more. In general, when they figure out how to support fast switching for some feature in IP, if that feature applies to another protocol, then they figure it out for that protocol too, but that's not necessarily true. Some router platforms support different types of switching than others. For example, some support distributed, autonomous, and optimum, and some don't. So, there is no way you could answer a simple question like what is the default switching method. I don't think you'll run into a question like that on the test anway. I believe the questions will be more general and test your understanding of the concepts of process versus faster switching methods. That area of the CIT class has been in need of fixing for years. I think the editors of the Cisco Press book should have fixed it up, but they just took the material from the course as is. Here's a URL to a good page on the subject of switching methods. It might not help with the test, which is dated and based on the inadequate discussion in the CIT class, but it will help you learn how it really works. http://www.cisco.com/warp/public/105/20.html _______________________________ Priscilla Oppenheimer www.troubleshootingnetworks.com www.priscilla.com Garrett Allen wrote: > > last minute prep question (and jitters) on how a router > switches traffic. > setting for the cit tomorrow. attempting to confirm my > understanding of > which type of switching is default for ip and which type for > ipx, appletalk, > etc. > > from ciscopress "cisco internetwork troubleshooting" by > chappell and farkas > chapter 3 > page 156 states that fast switching is the default switching > mechanism for all > protocols except ip. > page 157 states that optimium switching is the default > switching mechanism for > tcp/ip traffic. > question 3.5 at the end of the chapter asks "what is the > default switching > mechanism for ip traffic" and the given answer is "fast > switching is the > default switching mechanism for ip traffic" which is > contradictory. the cisco > site docs state optimum switching for ip and it makes sense > given the > underlying data structures (trie). > > then i run into the following question from a subscription > service which runs > counter to the whole lot > > "You have enabled priority queuing, custom queuing, or weighted > fair queuing. > Which traffic will always be classified by fast-switching logic? > > A - IP > > B - IPX > > C - AppleTalk > > D - DecNet > > Correct Answer - A > > IP traffic will always be classified by fast-switching logic. > All other > traffic will be process switched. Process switching means to > find a route. > Fast-switching logic puts the traffic in a cache." > > > > i'm guessing their talking about older versions of ios prior to > optimum > switching. > > > > arg, head hurts ..... > > thanks. > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=57633&t=57600 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
