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Point-to-Point Protocol

August 5th, 2017 in ROUTE 300-101 Go to comments

If you are not sure about PPP and PPPoE, please read my PPP tutorial and PPPoE tutorial.

Question 1


Password Authentication Protocol (PAP) is a very basic two-way process. The username and password are sent in plain text, there is no encryption or protection. If it is accepted, the connection is allowed. The configuration below shows how to configure PAP on two routers:

R1(config)#username R2 password digitaltut1
R1(config)#interface s0/0/0
R1(config-if)#encapsulation ppp
R1(config-if)#ppp authentication PAP
R1(config-if)#ppp pap sent-username R1 password digitaltut2
R2(config)#username R1 password digitaltut2
R2(config)#interface s0/0/0
R2(config-if)#encapsulation ppp
R2(config-if)#ppp authentication PAP
R2(config-if)#ppp pap sent-username R2 password digitaltut1

Note: The PAP “sent-username” and password that each router sends must match those specified with the “username … password …” command on the other router.

Question 2


Challenge Handshake Authentication Protocol (CHAP) periodically verifies the identity of the client by using a three-way handshake. The three-way handshake steps are as follows:

1. When a client contacts a server that uses CHAP, the server (called the authenticator) responds by sending the client a simple text message (sometimes called the challenge text). This text is not important and it does not matter if anyone can intercepts it.
2. The client then takes this information and encrypts it using its password which was shared by both the client and server. The encrypted text is then returned to the server.
3. The server has the same password and uses it as a key to encrypt the information it previously sent to the client. It compares its results with the encrypted results sent by the client. If they are the same, the client is assumed to be authentic.

Note: PPP supports two authentication protocols: PAP and CHAP.

Question 3

Question 4


PPP supports two authentication protocols: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). PAP authentication involves a two-way handshake where the username and password are sent across the link in clear text. For more information about PPP Authentication methods, please read Point to Point Protocol (PPP) Tutorial

Question 5

Question 6

Question 7

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  1. Sorlags
    November 15th, 2018

    Serously Oo

    I found a example like the exam here : https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/wan_frly/configuration/15-mt/wan-frly-15-mt-book/wan-pppofr.html#GUID-1CB0E01F-B4AF-4CF6-9863-D116BBD13C2B. I was the DTE exercise


    interface serial 0
    ” BLANK ”
    encapsulation frame-relay
    ” BLANK ” — I know there is 2 blank on interface serial 0 but I don’t rembemr the existing command and the blank

    #about sub-interface (it’s write like that in the exam)
    ” BLANK ”
    ” BLANK ”

    interface Virtual-Template1
    ip unnumbered ethernet 0
    ” BLANK ”

    D&D 1 : ” no ip address >
    D&D 2 : ” interface serial 0/0.1 point-to-point ”
    D&D 3 : ” interface serial 0/0.100 ”
    D&D 4 : ” frame-relay interface-dlci 32 ppp virtual-template1 ”
    D&D 5 : ” another think about virtual-template >
    D&D 6 : ” ip unnumbered ethernet 0 ”
    D&D 7 : ” ppp authentication chap ”
    D&D 8 : ” frame-relay lmi-type ansi ”


    interface serial 0
    ” no ip address ”
    encapsulation frame-relay
    ” frame-relay lmi-type ansi ”
    ” interface serial 0.1 point-to-point ”
    ” frame-relay interface-dlci 32 ppp virtual-template1 ”
    interface Virtual-Template1
    ip unnumbered ethernet 0
    ” ppp authentication chap ”

    I hope it’s will help you :)

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