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PPPoE Questions

August 4th, 2017 in ROUTE 300-101 Go to comments

Question 1

Explanation

PPPoE provides a standard method of employing the authentication methods of the Point-to-Point Protocol (PPP) over an Ethernet network. When used by ISPs, PPPoE allows authenticated assignment of IP addresses. In this type of implementation, the PPPoE client and server are interconnected by Layer 2 bridging protocols running over a DSL or other broadband connection.

PPPoE is composed of two main phases:
+ Active Discovery Phase: In this phase, the PPPoE client locates a PPPoE server, called an access concentrator. During this phase, a Session ID is assigned and the PPPoE layer is established.
+ PPP Session Phase: In this phase, PPP options are negotiated and authentication is performed. Once the link setup is completed, PPPoE functions as a Layer 2 encapsulation method, allowing data to be transferred over the PPP link within PPPoE headers.

Reference: http://www.cisco.com/c/en/us/td/docs/security/asa/asa92/configuration/vpn/asa-vpn-cli/vpn-pppoe.html

Question 2

Explanation

PPP Session Phase: In this phase, PPP options are negotiated and authentication is performed. Once the link setup is completed, PPPoE functions as a Layer 2 encapsulation method, allowing data to be transferred over the PPP link within PPPoE headers.

Reference: http://www.cisco.com/c/en/us/td/docs/security/asa/asa92/configuration/vpn/asa-vpn-cli/vpn-pppoe.html

Question 3

Explanation

The “dialer persistent” command (under interface configuration mode) allows a dial-on-demand routing (DDR) dialer profile connection to be brought up without being triggered by interesting traffic. When configured, the dialer persistent command starts a timer when the dialer interface starts up and starts the connection when the timer expires. If interesting traffic arrives before the timer expires, the connection is still brought up and set as persistent. An example of configuring is shown below:

interface Dialer1
ip address 12.12.12.1 255.255.255.0
encapsulation ppp
dialer-pool 1
dialer persistent

Question 4

Explanation

The “vpdn enable” command is used to enable virtual private dialup networking (VPDN) on the router and inform the router to look for tunnel definitions in a local database and on a remote authorization server (home gateway). The following steps include: configure the VPDN group; configure the virtual-template; create the IP pools.

Question 5

Explanation

There are three authentication methods that can be used to authenticate a PPPoE connection:

+ CHAP – Challenge Handshake Authentication Protocol
+ MS-CHAP – Microsoft Challenge Handshake Authentication Protocol Version 1 & 2
+ PAP – Password Authentication Protocol

In which MS-CHAP & CHAP are two encrypted authentication protocol while PAP is unencrypted authentication protocol.

Note: PAP authentication involves a two-way handshake where the username and password are sent across the link in clear text; hence, PAP authentication does not provide any protection against playback and line sniffing.

With CHAP, the server (authenticator) sends a challenge to the remote access client. The client uses a hash algorithm (also known as a hash function) to compute a Message Digest-5 (MD5) hash result based on the challenge and a hash result computed from the user’s password. The client sends the MD5 hash result to the server. The server, which also has access to the hash result of the user’s password, performs the same calculation using the hash algorithm and compares the result to the one sent by the client. If the results match, the credentials of the remote access client are considered authentic. A hash algorithm provides one-way encryption, which means that calculating the hash result for a data block is easy, but determining the original data block from the hash result is mathematically infeasible.

Question 6

Explanation

A PPPoE session is initiated by the PPPoE client. If the session has a timeout or is disconnected, the PPPoE client will immediately attempt to reestablish the session. The following four steps describe the exchange of packets that occurs when a PPPoE client initiates a PPPoE session:
1. The client broadcasts a PPPoE Active Discovery Initiation (PADI) packet.
2. When the access concentrator receives a PADI that it can serve, it replies by sending a PPPoE Active Discovery Offer (PADO) packet to the client.
3. Because the PADI was broadcast, the host may receive more than one PADO packet. The host looks through the PADO packets it receives and chooses one. The choice can be based on the access concentrator name or on the services offered. The host then sends a single PPPoE Active Discovery Request (PADR) packet to the access concentrator that it has chosen.
4. The access concentrator responds to the PADR by sending a PPPoE Active Discovery Session-confirmation (PADS) packet. At this point a virtual access interface is created that will then negotiate PPP, and the PPPoE session will run on this virtual access.

If a client does not receive a PADO for a preceding PADI, the client sends out a PADI at predetermined intervals. That interval is doubled for every successive PADI that does not evoke a response, until the interval reaches a configured maximum.

If PPP negotiation fails or the PPP line protocol is brought down for any reason, the PPPoE session and the virtual access will be brought down. When the PPPoE session is brought down, the client waits for a predetermined number of seconds before trying again to establish a PPPoE.

Reference: http://www.cs.vsb.cz/grygarek/TPS/DSL/pppoe_client.pdf

Question 7

Question 8

Question 9

Explanation

The picture below shows all configuration needed for PPPoE:

PPPoE_Topology_with_config.jpg

As we can see from the PPPoE Client configuration, to get the IP address assigned from the PPPoE server the command “ip address negotiated” should be used. For more information about PPPoE configuration please read our PPPoE tutorial.

Question 10

Explanation

According to this link: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/bbdsl/configuration/xe-3s/bba-pppoe-client.html

The PPPoE client does not support the following:
+ More than ten clients per customer premises equipment (CPE)-> This means a CPE can support up to 10 clients so answer A is correct.
+ Coexistence of the PPPoE client and server on the same device -> answer C is not correct

In the above link there is a topology shows “DMVPN Access to Multiple Hosts from the Same PPPoE Client” -> Answer B is correct.

Question 11

Comments
  1. Anonymous
    August 25th, 2017

    Failed today with 760pts….although I cleared all my labs , loads of new questions ,don’t trust any dumps…study hard chaps….and loads of simlet ( IPV6 , ACL, NAT, NAT-PT ETC ETC )

    ACL very important ( IPV6 and IPV4 both)

    I was using my old 642-902 books :(, please get the new cert guide for CCNP route 300-101)

  2. Anonymous
    September 22nd, 2017

    Passed today, the new dumps from IT-Libraries are perfect.
    If you go for the exam again check those dumps first.

  3. Mother of Dragos
    October 4th, 2017

    “please get the new cert guide for CCNP route 300-101” – Anon

    It’s rather useless, but will cover the basics. It does not go into enough detail on several topics and topics flat out are not in this “official” cert guilde.

    I failed by an even smaller margin and am pissed at the amount of material left out of the OCG, third party cert guides, CBT nuggets, etc. I’m feeling much better with reading articles and white papers that I find in the Cisco Learning Network or elsewhere.

  4. Maj
    October 16th, 2017

    Passed 9xx, really easy the new dumps from IT-Libraries are valid.
    My advice go over the study guides from IT-Libraries, practice the labs from here and in the meantime look for the dumps on this forum, there is a good changes that someone will share for free.

  5. Anonymous
    October 16th, 2017

    Please can you send IT-libraries dump at hocnav @ yahoo.com for 300-101

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