Lab 10. PPP Authentication Using CHAP (Method #2)

CCNA 200–301

Lab Objective:

The objective of this lab exercise is to configure two routers sharing a back-to-back Serial link encapsulated by PPP to authenticate each other using default CHAP parameters on Cisco IOS. By default, PPP connections are not authenticated or secured.

Lab Purpose:

PPP CHAP authentication configuration is a fundamental skill. One of the main reasons that PPP is so popular is because it has the capability to be secured and devices communicating using PPP can be authenticated. CHAP authentication is the most preferred method to secure PPP as it does not send usernames and passwords in clear text. As a Cisco engineer, as well as in the Cisco CCNA exam, you will be expected to know how to configure PPP CHAP authentication.

Task 1:

Configure the hostnames on R1 and R2 as illustrated in the topology.

Task 2:

Enable the Serial interfaces on R1 and R2. The Serial0/0 interface on R2 is identified as the DCE in the topology. Use the appropriate show command to verify that this interface is indeed the DCE. Configure the DCE interface on R2 to provide clocking to R1. The clock speed should be 768 Kbps. Verify that R1 receives clocking information from R2.

Task 3:

Enable PPP encapsulation on R1 and R2 Serial0/0 interfaces. Configure IP addressing on R1 and R2 Serial0/0 interfaces as illustrated in the topology.

Task 4:

Verify your interface encapsulation, which should be PPP by default. Test connectivity between R1 and R2 by pinging between the routers.

Task 5:

Configure PPP CHAP authentication on R1 and R2. Configure R1 to use the CHAP username Router1 with the password MyPass. Configure R2 to use the CHAP username Router2 with the password MyPass.

Task 6:

Enable PPP authentication debugging on R1. Next, perform a shutdown command followed by a no shutdown command on Serial0/0. Verify that you see the two routers authenticating each other via PPP CHAP. Disable debugging when you are done.

Task 1:

For reference information on configuring hostnames, please refer to earlier labs.

Task 2:

For reference information on verifying DTE/DCE status, please refer to earlier labs.

Task 3:

For reference information on enabling PPP encapsulation, please refer to earlier labs.

Task 4:

For reference information on verifying Serial encapsulation, please refer to earlier labs.

R1#ping 192.168.50.34

R2#ping 192.168.50.33

Task 5:

R1#conf t
R1(config)#int s0/0
R1(config-if)#ppp authentication chap
R1(config-if)#ppp chap hostname Router1
R1(config-if)#ppp chap password MyPass
R1(config-if)#exit
R1(config)#username Router2 password MyPass
R1(config)#end

R2#configure ter
R2(config)#interf ser0/0
R2(config-if)#ppp authentication chap
R2(config-if)#ppp chap hostname Router2
R2(config-if)#ppp chap password MyPass
R2(config-if)#exit
R2(config)#username Router1 password MyPass
R2(config)#end

NOTE: By default, there is no need to configure a hostname to be used for CHAP authentication on Cisco IOS routers as they will use the hostname configured on the router. However, to use a different hostname, CHAP must be configured for that. This is performed using the ppp chap hostname and ppp chap password commands on the PPP interface used for CHAP authentication.

Task 6:

R2#debug ppp authentication
R2#config t
R2(config)#int s0/0
R2(config-if)#shut
R2(config-if)#no shut
R2(config-if)#end
R2#undebug ppp authentication