New CCNA PPP Questions & Answers with Explanation.

By | August 14, 2017

This is an Updated  CCNA exam question (October 2017). You might see a different IP addressing,  Port allocation and PPP Configurations.

As usual, take time to read through the question so as to clearly understand what you are required to do. Read TWICE or even THRICE.

Note: This PPP Questions and Answers are used for demonstration purpose only, you will see different IP addressing,  configuration and Port allocation in the real CCNA exam. But it all works the same way, try and understand the technique.

I suggest you use packet tracer for practice.

Question 1
Which PPP subprotocol negotiates authentication options?

Answer: D

There are different PPP suite protocols, the single most important protocol is the PPP Link Control Protocol (LCP). The Link Control Protocol (LCP) is documented in RFC 1661.
LCP is the chief controller protocol of PPP; it is responsible for its overall successful operation.

LCP negotiates link for PPP parameters to dynamically configure the data link layer of a connection. Common LCP options include the PPP MRU, the authentication protocol, compression of PPP header fields, callback, and multilink options.
There are three main stages of “link life” and LCP plays a key role in each one:

Link Configuration: The process of setting up and negotiating the parameters of a link.

Link Maintenance: The process of managing an opened link.

Link Termination: The process of closing an existing link when it is no longer needed.

Question 2

In the following exhibit, what does the line “LCP closed” mean?

A. The LCP process has completed.

B. The router does not have an IP address configured.

C. The serial line is disconnected.

D. The LCP process has not completed.

Answer D.


The LCP closed line states that the LCP process has not completed. This could be due to numerous reasons, such as conflicting options or authentication failure.

Question 3

During which phase of PPPoE is PPP authentication performed?

A. the PPP Session phase

B. Phase 2

C. the Active Discovery phase

D. the Authentication phase

E. Phase 1

Answer: A


 PPPoE is composed of two main phases:

1.    Active Discovery Phase: this is when the PPPoE client locates a PPPoE server, called an access concentrator. The process here is to assign a Session ID which enables the PPPoE layer to be established.

2.    PPP Session Phase:  PPP options are negotiated and authentication is made. 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: vpn-cli/vpn-pppoe.html

Question 4
As a network administrator, you were asked to configure a serial link between the main office and a remote location. The router at the remote office is a non-Cisco router. How would you configure the serial interface of the main office router to make the connection?

A. Main(config)# interface serial 0/0
Main(config-if)# ip address
Main(config-if)# no shut

B. Main(config)# interface serial 0/0
Main(config-if)# ip address
Main(config-if)# encapsulation ppp
Main(config-if)# no shut

C. Main(config)# interface serial 0/0
Main(config-if)# ip address
Main(config-if)# encapsulation frame-relay
Main(config-if)# authentication chap
Main(config-if)# no shut

D. Main(config)# interface serial 0/0
Main(config-if)#ip address
Main(config-if)#encapsulation ietf
Main(config-if)# no shut

Answer: B

Question 5

 In the following exhibit, Router A will not form a PPP connection with Router B.

What seems to be the error?

A. The username on Router A should match Router A’s hostname and the

      username on Router B should match Router B’s hostname.

B. The bandwidth should be configured the same on both routers.

C. The interfaces on Router A and Router B should be matching for authentication


D. The encapsulation on both routers should be configured as PPP.

Answer D.


This configuration has an encapsulation mismatch. Router A is configured to use the PPP encapsulation protocol. Router B defaults to the HDLC protocol because no encapsulation is configured.

Question 6
Which two options are valid WAN connectivity methods? (Choose two)
D. L2TPv3
E. Ethernet

Answer: A C

Question 7
Which Layer 2 protocol encapsulation type supports synchronous and asynchronous circuits and has built-in security mechanisms?
C. X.25
D. Frame Relay

Answer: B
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

Question 8

 In the following exhibit, Router A is configured for PPP multilink to Router B. However, the multilink is not functioning properly. What is the problem?

Question 9
Which of the following command is used to enable CHAP authentication with PAP as the fallback method on a serial interface?
A. (config-if)# authentication ppp chap fallback ppp
B. (config-if)# authentication ppp chap pap
C. (config-if)# ppp authentication chap pap
D. (config-if)# ppp authentication chap fallback ppp

Answer: C
The command “ppp authentication chap pap” command indicates the CHAP authentication is used first. If it fails or is rejected by the 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 10
Which of the following describes the roles of devices in a WAN? (Choose three.)
A. A CSU/DSU terminates a digital local loop
B. A modem terminates a digital local loop
C. A CSU/DSU terminates an analog local loop
D. A modem terminates an analog local loop
E. A router is commonly considered a DTE device
F. A router is commonly considered a DCE device

Answer: A D E

This is one of the fundamentals of networking.
The idea behind a WAN is to be able to connect two DTE networks together through a DCE network. The network’s DCE device (includes CSU/DSU) provides clocking to the DTE-connected interface (the router’s serial interface).

Question 11
Which two statements about using the CHAP authentication mechanism in a PPP link are true? (Choose two)
A. CHAP uses a two-way handshake.
B. CHAP uses a three-way handshake.
C. CHAP authentication periodically occurs after link establishment.
D. CHAP authentication passwords are sent in plaintext.
E. CHAP authentication is performed only upon link establishment.
F. CHAP has no protection from playback attacks.

Answer: B C


 CHAP is an authentication method used by Point to Point Protocol (PPP) configured servers to validate the identity of remote clients. CHAP periodically verifies the identity of the client by using a three-way handshake. This happens at the time of establishing the initial link (LCP) and may happen again at any time afterward. The verification is based on a shared secret (such as the client user’s password).

Question 12
Which of the following are key characteristics of PPP? (Choose three.)
A: can be used over analog circuits
B: maps Layer 2 to Layer 3 address
C: encapsulates several routed protocols
D: supports IP only
E: provides error correction

Answers: A C E

Question 13

What can a network administrator benefit by using PPP Layer 2 encapsulation? (Choose three.)
A: VLAN support
B: compression
C: authentication
D: sliding windows
E: multilink support
F: quality of service

Answers: B C E

Question 14

At which layer of the OSI model does PPP perform?

A. Layer 2

B. Layer 3

C. Layer 4

D. Layer 5

Answer: A


 The Point-to-Point Protocol (PPP) operates in the layer 2 of the OSI model. It provides a standard process for transporting multi-protocol datagrams over point-to-point links. PPP originally emerged as an encapsulation protocol for transporting IP traffic between two peers.

Question 15

You need to set up PPP authentication for RouterA. The adjoining router is named RouterB, and both routers will have a matching password of cisco. Which commands will achieve this?

A. RouterA(config)#username RouterA password cisco

     RouterA(config)#interface serial 0/1/0

     RouterA(config-if)#ppp authentication chap pap

     B. RouterA(config)#username RouterB password cisco

     RouterA(config)#interface serial 0/1/0

     RouterA(config-if)#ppp authentication chap pap

C. RouterA(config)#username RouterA cisco

     RouterA(config)#interface serial 0/1/0

     RouterA(config-if)#ppp authentication chap pap

D. RouterA(config)#username RouterA password cisco

     RouterA(config)#interface serial 0/1/0

     RouterA(config-if)#authentication chap pap

Answer  B.


The first step is to set the username of RouterB to use for authentication via username RouterB password cisco. Then enter the interface and configure authentication with the command ppp authentication chap pap.