PPP Flashcards
Question 1
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
Question 2
A network administrator needs 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 should the network administrator 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 172.16.1.1 255.255.255.252 Main(config-if)# no shut
B. Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252 Main(config-if)# encapsulation ppp Main(config-if)# no shut
C. Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252 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 172.16.1.1 255.255.255.252 Main(config-if)#encapsulation ietf
Main(config-if)# no shut
Answer: B
Question 3
Refer to the exhibit:
The Bigtime router is unable to authenticate to the Littletime router. What is the cause of the problem?
A. The usernames are incorrectly configured on the two routers.
B. The passwords do not match on the two routers.
C. CHAP authentication cannot be used on a serial interface.
D. The routers cannot be connected from interface S0/0 to interface S0/0.
E. With CHAP authentication, one router must authenticate to another router. The routers cannot be configured to authenticate to each other.
Answer: B
Question 4 What is the benefit of point-to-point leased line? A. Low cost B. Full-mesh capability C. Flexibility of design D. Simply configuration
Answer: D
Question 5 When you deploy multilink PPP on your network, where must you configure the group IP Address on each device? A. In the global config B. Under serial interface C. Under the routing protocol D. Under the multilink interface
Answer: D
Question 6 What are two authentication types of MLPPP? A. PEAP B. LEAP C. PAP D. CHAP E. TACACS+
Answer: C D
Question 7 At which layer of the OSI model does PPP perform? A. Layer 2 B. Layer 3 C. Layer 4 D. Layer 5 E. Layer 1
Answer: A
Question 8
Which 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
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.
orrect Answer: BC Explanation: Understanding and Configuring PPP CHAP Authentication http://www.cisco.com/en/US/tech/tk713/tk507/technologies_tech_note09186a00800b4131.shtml One-Way and Two-Way Authentication CHAP is defined as a one-way authentication method. However, you use CHAP in both directions to create a two-way authentication. Hence, with two-way CHAP, a separate three-way handshake is initiated by each side. In the Cisco CHAP implementation, by default, the called party must authenticate the calling party (unless authentication is completely turned off). Therefore, a one-way authentication initiated by the called party is the minimum possible authentication. However, the calling party can also verify the identity of the called party, and this results in a two-way authentication. One-way authentication is often required when you connect to non-Cisco devices.
At which layer of the OSI model does PPP perform?
A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 5
Correct Answer: A
Explanation: Point-to-Point Protocol (PPP) is a data link protocol commonly used in establishing a direct connection between two networking nodes. It can provide connection authentication, transmission (using ECP, RFC 1968), and compression. encryption
Which command is used to enable CHAP authentication, with PAP as the fallback method, on a serial interface?
A. Router(config-if)# ppp authentication chap fallback ppp
B. Router(config-if)# ppp authentication chap pap
C. Router(config-if)# authentication ppp chap fallback ppp
D. Router(config-if)# authentication ppp chap pap
Correct Answer: B
Which Layer 2 protocol encapsulation type supports synchronous and asynchronous circuits and has built-in security mechanisms?
A. HDLC
B. PPP
C. X.25
D. Frame Relay
Correct Answer: B
Explanation: High-Level Data Link Control (HDLC) – HDLC is the default encapsulation type on point-to- point, dedicated links, and circuit-switched connections. It is used typically when communicating between two Cisco devices. It is a bit-oriented synchronous data link layer protocol. Point-to-Point Protocol (PPP) – Provides router-to-router and host-to network connections over synchronous and asynchronous circuits. PPP was designed to work with several network layer protocols, such as IP, and IPX. PPP also has built in security mechanisms such as PAP and CHAP X.25/Link Access Procedure, Balanced (LAPB) – ITU-T standard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in public data networks. X.25 specifies LAPB, a data line layer protocol. X.25 is a predecessor to Frame Relay. Frame Relay – Industry standard, switched data link layer protocol that handles multiple virtual circuits. It is a next-generation to X.25 that is streamlined to eliminate some of the time- consuming processes (such as error correction and flow control) that were employed in X.25.
QUESTION 79
Which PPP subprotocol negotiates authentication options?
A. NCP
B. ISDN
C. SLIP
D. LCP
E. DLCI
Hide Answer
Correct Answer: D Section: WAN Technologies
Hide Explanation
Explanation: A protocol that establishes, configures, and tests data link connections used by the PPP Link Control Protocol offers PPP encapsulation different options, including the following: Authentication – options includes PAP and CHAP Compression – Data compression increases the throughput on a network link, by reducing the amount of data that must be transmitted. Error Detection -Quality and Magic numbers are used by PPP to ensure a reliable, loop-free data link. Multilink – Supported in IOS 11.1 and later, multilink is supported on PPP links between Cisco routers. This splits the load for PPP over two or more parallel circuits and is called a bundle.
