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路由教程复习 ROUTE Set 1

创建于: 2009-12-19 12:21:53          

路由教程复习 ROUTE Set 1

Route就是用来显示、人工添加和修改路由表项目的。大多数主机一般都是驻留在只连接一台路由器的网段上。由于只有一台路由器,因此不存在使用哪一台路由器将数据包发表到远程计算机上去的问题,该路由器的IP地址可作为该网段上所有计算机的缺省网关来输入。 但是,当网络上拥有两个或多个路由器时,你就不一定想只依赖缺省网关了。实际上你可能想让你的某些远程IP地址通过某个特定的路由器来传递,而其他的远程IP则通过另一个路由器来传递。


Review Questions

The following review questions are taken from the current ROUTE curriculum. These review questions do not reflect the actual questions you will receive on the live certification exam. They are only meant to supplement your learning experience.


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评论 (9)
  • sam_

    sam_  说: 2014-08-03 16:40:19


  • shfhbxg

    shfhbxg  说: 2012-02-27 18:23:29


  • Paul Sa

    Paul Sa  说: 2010-10-27 07:50:21

    You might want the full routing table because one isp might have a better path to the destination as opposed to a default route which might take you through a longer path.? This would increase performance to your site. If you’re hosting you might want to consider full route table otherwise a default route should suffice.? This is in reference as to why you would want a full route table.

  • rboldy

    rboldy  说: 2010-09-20 12:59:45

    This is a classic cisco "trick', a way to ensure that cadidates understand more that just what the question can ask if specific right or wrong answers were given. This kind of question is designed to do exactly what it did for you. That is to ensure that the only way to answer the question correctly wiithout guessing is to know 100% that all the other three answers are not true.

    The term "AS routing policy" isn't a term that is used in the book but it illudes to using the "policy" of using AS PATH to determine best "routing" path, which IS correct. The other answers ARE either terms that are used for other things OR are incorrect because they are a wrong explaination of a correct term. The illuded term is made to sound like something else i.e. "policy based routing" to make you second guess this in order that if you had any doubt about the other three being incorrect you might not be certain this was the right answer.

    One could say that "AS routing policy" is the creation of a routing policy to forward packets based on the AS PATH attribute which in turn could be said to be something that BGP uses by default during the best path selection process.

    Personally I think this is pretty poor form. The intent is to ensure that you fully understand the subject matter but the result is often to confuse and destroy confidence. Always trust the wording of the question and any answer to be verbose, even though "AS routing policy" isn't a standardized term it does mean something.

    In the same way "number of routers to reach a destination network" also means something and is very precise. It is clear that this option in the answer is testing your ability to understand that an AS_PATH is not a list of specific routers but a list of Autononous Systems that are made up of an indeterminate number of routers.

  • S Page

    S Page  说: 2010-09-20 07:34:07

    Don't understand the use of the term? "AS routing policy", or I should say that I haven't come across this term in the Cisco press book.? It seems like the term means the same as "Policy-based Routing", but if that's true, then I don't understand how this is the correct answer for question #17:

    17. What does BGP use during the best path selection process?
    ???????? speed
    ???????? AS routing policy
    ???????? bandwidth plus delay
    ???????? number of routers to reach a destination network

    I just chose that answer because I knew the other answers were not correct.

  • rboldy

    rboldy  说: 2010-09-13 23:27:02

    I agree with Richard,

    I work for a SP and we provide the option to get more that just a default route to our dual-homed BGP customers. The reason is that most customer want to send traffic to desinations that are local to us (i.e routes that belong to our AS or are sourced from it) directly to us, regardless of where they want the rest of their internet traffic to go.

    In this way they can chose a default route from the other provider as primary but chose local routes from us over this default.

    In order to keep the routing symetric they still AS prepend their routes to us - making them less prefered - but also send us an pre-determined community String that set's the local-preference of these routes to be higher on our network - making them more prefered locally, but not after we advertise them to our upstream AS, as Local-Preference isn't honored over an eBGP peer.

  • David Spiro Valentine

    David Spiro Valentine  说: 2010-05-31 08:44:12

    Really good set of questions... Mostly on BGP though I thought there would be like a mixture of questions in order to try emulate a real exam experience although as the disclaimer has stated, they are just for our learning purposes only.

    On to ROUTE Set 2

  • Andreas Huelsbeck

    Andreas Huelsbeck  说: 2010-05-24 22:18:14

    hello richard,

    this is a real live example: last time a customer want?s the full routing table and our engineer says do you have enough memory and is your router scalable enough? the customer says yes it has. than he get?s the full routing table ca. 312.000 routes and his router reboots because he haven?t enough memory. why do you want more than a default route? okay you can make as-path prepending with your own as but a service provider will filter this out by default (security for other as). why do you want more than a default route?

    from your "two" sp?s? this is no "i said it" its a real question i?m working at a service provider. my view is a little bit focused. thanks for your answer.

    Greets Andreas

  • richard jackson

    richard jackson  说: 2010-03-25 08:07:51

    Not sure I agree with all of the answers.

    An enterprise network dual home to 2 ISPs wants to learn more than the default. They want the networks in each ISP to use direct access to those networks