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ICND2 – WAN Questions

March 23rd, 2017 in ICND2 200-105 Go to comments

Question 1

Question 2

Explanation

Point-to-Point Protocol (PPP) can use either Password Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol (CHAP) for authentication. CHAP is used upon initial link establishment and periodically to make sure that the router is still communicating with the same host. CHAP passwords arc exchanged as message digest algorithm 5 (MD5) hash values.

The three-way handshake steps are as follows:

Challenge: The authenticator generates a frame called a Challenge and sends it to the initiator. This frame contains a simple text message (sometimes called the challenge text). The message has no inherent special meaning so it doesn’t matter if anyone intercepts it. The important thing is that after receipt of the Challenge both devices have the same challenge message.

Response: The initiator uses its password (or some other shared “secret” that the authenticators also knows) to encrypt the challenge text. It then sends the encrypted challenge text as a Response back to the authenticator.

Success or Failure: The authenticator performs the same encryption on the challenge text that the initiator did. If the authenticator gets the same result that the initiator sent it in the Response, the authenticator knows that the initiator had the right password when it did its encryption, so the authenticator sends back a Success message. Otherwise, it sends a Failure message.

(Reference: CCNA Quick Reference Sheets)

Question 3

Explanation

From the output, we see the the line “Serial0/1 is up, line protocol is up”. That means the link is good and the interface is functioning normally. Also the encapsulation used on this interface is HDLC -> The other end must use the same encapsulation. Otherwise the line protocol will go down.

Question 4

Question 5

Explanation

The command “ppp authentication chap pap” command indicates the CHAP authentication is used first. If it fails or is rejected by other side then uses PAP instead. If you want to use PAP first (then CHAP) you can use the “ppp authentication pap chap” command.

Question 6

Question 7

Explanation

PPP supports both synchronous (like analog phone lines) and asynchronous circuits (such as ISDN or digital links). With synchronous circuits we need to use clock rate.

Note: Serial links can be synchronous or asynchronous. Asynchronous connections used to be only available on low-speed (<2MB) serial interfaces, but now, there are the new HWICs (High-Speed WAN Interface Cards) which also support asynchronous mode. To learn more about them please visit http://www.cisco.com/en/US/prod/collateral/modules/ps5949/ps6182/prod_qas0900aecd80274424.html.

Question 8

Question 9

Explanation

Link Control Protocol (LCP) is a subprotocol within the Point-to-Point Protocol protocol suite that is responsible for link management. During establishment of a PPP communication session, LCP establishes the link, configures PPP options, and tests the quality of the line connection between the PPP client and PPP server. LCP automatically handles encapsulation format options and varies packet sizes over PPP communication links.

LCP also negotiates the type of authentication protocol used to establish the PPP session. Different authentication protocols are supported for satisfying the security needs of different environments.

Other subprotocol within PPP is Network Control Protocol (NCP), which is used to allow multiple Network layer protocols (routed protocols) to be used on a point-to-point connection.

Question 10

Explanation

Layer 2 includes the popular WAN standards, such as the Point-to-Point Protocol (PPP), High-Level Data-Link Control (HDLC) and Frame Relay protocols.

Question 11

Question 12

Question 13

Question 14

Comments (11) Comments
  1. Sunrise
    April 8th, 2017

    On question 8, PPP is an encryption method. Is it also a WAN connectivity method?
    Ethernet is used for both LAN and WAN nowadays. Or am I mistaken?

  2. Sunset
    May 22nd, 2017

    ISP’s use PPP(oE) to establish a connection between customer and ISP if, the customer has no IP address and is requesting one from the ISP.. it gives you the option to use CHAP which is ideal for ISP-Customer communication.. correct me if I’m wrong please 🙂

  3. smitty
    May 24th, 2017

    PPP is a layer 2 protocol for serial links (Cisco default is HDLC). PPP does not have the ability to encrypt data inherently. It does have built in authentication however options being PAP or CHAP. PAP passes passwords in clear text, while CHAP uses a hash to hide the password. PPP(oE) will use CHAP for authentication.

  4. Pete
    June 16th, 2017

    Why can’t I see the questions?

  5. lloyd
    June 19th, 2017

    Why is C wrong to Question 3? Seems like it is also correct.

  6. Mr. Dunde
    June 28th, 2017

    In Q3 the answer C is a distraction. The main focus is related to the encapsulation and the interface state (up/up). If the interface state is up/up then same encapsulation are used in the other end of the link. Note the Keepalive setting, is the default (10) seconds. If this setting are not the same, then the state would be different up/down. IP address and mask is another story we are talking about L2 not L3.

  7. Mr. Dunde
    June 28th, 2017

    In Q8, PPP is a protocol used to serial links and the Q is pointing to ((((connectivity methods)))). DSL clearly is a connectivity method. Many new technologies are using Ethernet for WAN connection like MPLS and MetroEthernet etc. For me the correct answers are C and E. The Q is obscure in essence.

  8. no
    July 30th, 2017

    @Mr.Dundee — I was just reviewing (for the millionth time) for ICND2 tomorrow, and I agree with you, in part. PPP is certainly a WAN connectivity “method,” but Ethernet (as in PPPoE) is also good.

    My only guess is that for greater specificity they want you to associate DSL in the same conceptual bucket.

    I guess I can live with DSL and PPP, but would welcome any thoughts. Definitely not WAP or L2TP, so that narrows it down, at least!

  9. no
    July 30th, 2017

    I think the key is that their using the kind of weasel/semi-ambiguous word “method,” so who knows.

  10. no
    July 30th, 2017

    Also, on question 9, icnd2PDF.pdf states LCP is “negotiate control options,” but here, if I’m reading it right, the correct answer is given, namely that LCP is concerned with authentication, and NCP handles multiple protocols.

    I’m pretty sure I’m not wrong, but corrections welcome.

  11. interface
    August 4th, 2017

    I cant see any of the questions. How do i go about getting access to them?