http://www.cisco.com/warp/public/471/ppp_authen_ts_fl.html
MD/DES Compare Failed
BR0:1 CHAP: I RESPONSE id 16 len 33 from "maui-soho-03"
BR0:1 CHAP: O FAILURE id 16 len 25 msg is "MD/DES compare failed"
This error is caused by a password mismatch. This could be cause by two reasons:
The peer did not supply the password expected by the local router. For example, we expected (and configured) the password LetmeIn, but the peer used the password letmein. You can either re-configure the username and password sent by the peer or correct the peer with the right username.
The local router does not have the password correctly configured. If you have verified that the password supplied by the peer is correct, then reconfigure the local router.
Solution:
Remove the existing username and password entry using the command:
no username <username>
where <username> is replaced by the username in the error message. In this example, that would be maui-soho-03.
Configure the username and password using the command:
username <username> password <password>
The username should be the same as in the CHAP message shown above. The password should match the password on the remote router.