Seems like recent Windows versions has enabled some security options which Rdesktop can’t handle.
ERROR: CredSSP: Initialize failed, do you have correct kerberos tgt initialized ?
Failed to connect, CredSSP required by server.
The solution is to use XFreeRDP, but the syntax of the arguments parameters are quite uncommon… Example:
% xfreerdp /u:firstname.lastname@example.org /p:password /w:1366 /h:768 /v:192.0.2.1
connected to 192.0.2.1:3389