I am not getting this task.Why "ppp pap sent-username Rack1R4 password 0 CISCO" is not used in R4.
It is only used in R5.Please give me a detailed explanation how this authentication is working?
Thanks and Regards
Mandatory minimum options for configuring PAP are 1) specifying which node (server) requests identity (R4 in that case) 2) specifying username/password on the client (R5) through "ppp pap sent-username" command.
In case of CHAP (in this example) you don't need to configure "ppp chap username" under interface configuration cause by default (when using CHAP!) client (R4 in that case) reply is labeled using its own hostname (RACK1R4) - this is the task requirement. If the server needs to accept any other user/pass - you should configure it through the "ppp chap hostname" command on the client and have the same user/pass in the server configuration at the same time.
Here are the links describing the behavior:
PAP : http://www.cisco.com/en/US/tech/tk713/tk507/technologies_tech_note09186a0080093c6f.shtml
CHAP : http://www.cisco.com/en/US/tech/tk713/tk507/technologies_tech_note09186a00800b4131.shtml