Engineering Journal 4.3.3:  Adding a username

You should add a username entry for each remote system with which the local router communicates.  You should also add a username entry for each remote system from which the local router requires authentication.  Finally, the remote device must also have a username entry for the local router.  

To enable the local router to respond to remote CHAP challenges, one username entry must be the same as the host name entry that has already been assigned to the device. With CHAP, you should use secret passwords that are known only to the authenticator and peer.