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I'm studying for CCNA 2 exam. Here's one of the questions. I already know the answer. What I am looking for is the reason why the incorrect answers are...incorrect. =)

For example, the question is:

What is the purpose of a routing protocol?

  • A) It is used to build and maintain ARP tables.
  • B) It provides a method for segmenting and reassembling data packets.
  • C) It allows an administrator to devise an addressing scheme for the network.
  • D) It allows a router to share information about known networks with other routers.
  • E) It provides a procedure for encoding and decoding data into bits for packet forwarding.

The answer is D).

  • A) I believe A) is false because routing protocols are used to build and maintain routing tables, not ARP tables.
  • B) Regarding B), I think segmenting and reassembling data packets would be enabled by Transmission Control Protocol (TCP), right?
  • C) Would this be Internet Protocol?
  • D) TRUE
  • E) What about this one?
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Hm… I think this is borderline off-topic, although the FAQ mentions "I would like others to explain ______ to me". So let's see. –  slhck Sep 19 '11 at 21:48
    
@slhck The FAQ directs that questions should be about computer software. Questions can be asked in many forms, one of which is "I would like other to explain ... to me". Routing protocols are standards, not software. If this question was about manipulating routing protocols with specialized software (like packet inspection, and getting it to work), it would have been on topic in my point of view. –  Duijf Sep 19 '11 at 21:57
    
While D is correct, it doesn't fully answer the question. –  Matt H Sep 19 '11 at 22:01
    
With reference to the FAQ, I suggest this gets clobbered by "You should only ask practical, answerable questions based on actual problems that you face. Chatty, open-ended questions diminish the usefulness of our site and push other questions off the front page." Voted to close. –  Linker3000 Sep 19 '11 at 22:09
    
@Linker3000 This is a constructive question, routing protocols were built for a specific purpose, which is asked for and therefore answerable in the Q&A format the FAQ prescribes. It is off-topic though, see my previous post. –  Duijf Sep 19 '11 at 22:16
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closed as off topic by Linker3000, Randolph West, 8088, Nifle, Tom Wijsman Sep 20 '11 at 19:01

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1 Answer

There is no such thing as encoding and decoding data into bits for packet forwarding. Frames are always encoded/decoded in the physical layer, no matter if they are to be used in routing or anything else. Routing protocol is implemented so the packets can be traced through two or more different networks. For ensuring the right path for any travelling packet.

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