Thank you a lot, Alan DeKok, you've pointed exactly to the error.
Because you started the server using a different IP and port than what's in the configuration files, it's not using the "default" virtual server.
When started the server without -i and -p parameters, the radtest test passes and my external client works too. With both v. 3.2.x and 3.0.20. Could someone point me to documentation on how to change the default port? As the -p option must go with -i we have to specify the interface, even if it is localhost. When I start the server with default port, as: freeradius -X -i 127.0.0.1 -p 1812 or freeradius -X -i localhost -p 1812 the radtest test fails. A comment in sites-available/default : "The server ignore all "listen" section if you are using '-i' and '-p' # on the command line." suggests that command line options have preference - but instead nothing works at all. With all respect, this does not meet the "least surprise to the user" principle. --