Sunday, March 26, 2006


PPP CHAP authentication. (Question #48)

Consider the following debug ouput from debug ppp authentication

*Mar 27 06:06:59.357: %LINK-3-UPDOWN: Interface Serial4/0:0, changed state to up
*Mar 27 06:06:59.477: Se4/0:0 PPP: Using dialer call direction
*Mar 27 06:06:59.477: Se4/0:0 PPP: Treating connection as a callout
*Mar 27 06:06:59.477: Se4/0:0 PPP: Authorization NOT required
*Mar 27 06:06:59.477: Se4/0:0 PPP: No remote authentication for call-out
*Mar 27 06:06:59.537: Se4/0:0 CHAP: I CHALLENGE id 25 len 28 from "Router2"
*Mar 27 06:06:59.597: Se4/0:0 CHAP: Using hostname from interface CHAP
*Mar 27 06:06:59.597: Se4/0:0 CHAP: Using password from AAA
*Mar 27 06:06:59.597: Se4/0:0 CHAP: O RESPONSE id 25 len 28 from "Router1"
*Mar 27 06:06:59.709: Se4/0:0 CHAP: I SUCCESS id 25 len 4

The debug output has some text indicating that authentication is required but then some authentication seems to happen anyway. What must have been configured on the router for such behavior?

This router R1 probably has "ppp direction callout" and still has the username Router2 password cisco.

I think that in addition it would also need the following for authorization:

aaa new-model
aaa authorization network aaa_aur none
aaa session-id common

interface Async65
ip address ...
encapsulation ppp
ppp authorization aaa_aur
ppp direction callout
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Hope this helps!

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