I want to use HTTrack to make mirror copy of my new modem-router's web
interface. The modem is a TPLink-AC1600, but internally it is named Archer
VR1600v. It's not yet in use for internet access (its awaiting installation of
a new fibre broadband service), but I am able to browse its web interface in
the meantime by connecting it directly to a PC.

I have successfully used HTTrack to do the same with my previous modem-router,
which is for my current ADSL service, but it won't do it for the new modem. I
suspect its because the first page displayed by the modem requires entry of a
username and password. (It's a form on the main page; not a pop-up.)

Can I make HTTrack supply the username and password before attempting the
download?