Hello Sandro
Indeed, it seems that this command does not show any output. I’m not sure if this is an issue simply due to a more restrictive implementation of debugging on IOS 15.X and later, or if it has to do with older versions as well. In any case, it would be interesting to test this out with various IOS versions just to see the results.
Looking a little bit in more detail at the Cisco Command Reference for this command, it seems to indicate that the debug condition command works on an interface level. Specifically it says:
Use the debug condition command to restrict the debug output for some commands. If any debug condition commands are enabled, output is generated only for interfaces associated with the specified keyword.
Although not completely clear, it seems to indicate that it is a prerequisite that the interface be specified in addition to any other parameters such as IP address. It may be worth experimenting with!
I hope this has been helpful!
Laz