Cisco CCNA mock exam questions sample test – Question 16

.You are configuring a WAN connection between two offices. You cannot ping between the routers in a test. The Serial0 interface on RouterA is connected to the Serial1 interface on
RouterB.
The commands you have executed are shown below. What is the problem with the configuration?

A. The passwords are incorrectly configured
B. The usernames are incorrectly configured
C. The wrong interface has been configured
D. The encapsulation is incorrect on RouterA
E. The encapsulation is incorrect on RouterB
F. The authentication types do not match

Correct Answer: C

Explanation:
The two routers are connected using Serial0 on RouterA and Serial1 on RouterB. However, the configuration commands were executed on interface Serial0 on RouterB. So although
the configuration itself is completely correct, it is configured on the wrong interface.
The passwords are correct. The passwords should match on both routers. In this case, they are both set to lie. If even one character does not match, including character casing, the
authentication and the connection will fail.
The usernames are correct. The username should be set to the host name of the peer router. In this case, RouterA’s username is set to RouterB and RouterB’s username is set to
RouterA, which is correct.
The encapsulations are correct. They are both set to PPP, which is the correct type of encapsulation when using authentication.
The authentication types do match. They are both set to CHAP. It is possible to configure two authentication methods, with the second used as a fallback method in cases where the
other router does not support the first type. The command below would be used to enable CHAP with PAP as a fallback method:
RouterB(config-if)#ppp authentication chap pap
Objective:
WAN Technologies
Sub-Objective:
Configure and verify PPP and MLPPP on WAN interfaces using local authentication
References:
Cisco > Home > Support > Technology Support > WAN > Point-To-Point Protocol (PPP) > Design > Design Technotes > Understanding and Configuring PPP CHAP Authentication