Reasons for "MS-CHAP2-Response is incorrect"

Alan DeKok aland at
Fri Jul 12 15:58:47 CEST 2019

On Jul 12, 2019, at 10:10 AM, Sven Hartge <sven at> wrote:
> The 1st level support group here has asked me to clarify the reasons
> behind authentication errors where the message is "mschap:
> MS-CHAP2-Response is incorrect" so they can better point the end users
> in the right direction.
> The obvious one is of course "wrong password", another one is "mucking
> about with the Username in the RADIUS server" (which I don't do).
> What other reasons are there for this error type to occur?

  Pretty much just those two.

  Other options are things like "calculating MS-CHAP wrong", which some systems do.  But not FreeRADIUS. :)

  Alan DeKok.

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