I have this printer. My reading of the manual was that it will operate in only
one of the three modes at a time. I have mine wired to my router, which is the
only thing which never gets turned off. Works great from Ubuntu and Windows.

I had to install Brother's Admin Professional (from their web site) on the
Windows machine to tell the printer to use a static IP address, since Ubuntu
likes network printers to have static addresses.

After I sent it I started reading the manual and
yes, I found basically 1 line that say either or but not both. Now all I
have to do is figure out how to either turn off the wireless access so
wired access starts up or figure out how to let my desktops access the
printer as a wireless device.

Yesterday I did a google on "linux brother hl-2170w" and was led to the
Linux foundation web site. Folowing instructions I eventually got to
"openprinting.org" and the recommended driver called pxlmono. I followed
instructions and now I have Linux talking to the printer and able to
print via wireless. I did the same for my Debian computer and now have
both being able to print. To make sure I was printing via wireless I
disconnected the network cable. No problems. Now to get my WinXP laptop
working properly via wireless.