Hi Steve!
you are perfeclty right!
I have Dns forwarder enabled, and I've seen the description (under dhcp server -> Dns servers):
NOTE: leave blank to use the system default DNS servers - this interface's IP if DNS forwarder is enabled, otherwise the servers configured on the General page.
but I admit I didn't understand the full meaning: maybe that "dash" misleaded me…. :-[
Thanks again for your reply!!
Aronese