Not all devices on C7000v2 see each other

> I've wired, via Ethernet through Gb switches: my laptop, a printer,
> and a Chromecast ready TV; [...]

> [...] if I turn wifi off on our Dell printer, [...]

   I'll assume that your (unspecified) "a printer" and your
(unspecified) "our Dell printer" are the same thing.

   Does that mean that the printer is always connected by Ethernet, and
sometimes also wirelessly?

> [...] no one on the LAN (wired or wireless) can see it.

   "see"?  Where/how, exactly, are they looking for it?

   Generally speaking, a _device_ (like, say, a printer) does not have
an IP address; a network _interface_ on a device has an IP address.  If
your computers/devices are expecting to find the printer at the IP
address of its wireless interface, and you disable that interface, then
they might very easily not guess that the same printer can be found at
the (different) IP address of its Ethernet interface.

   For a device with only one network interface, you can afford to be
sloppy, and refer to the address of the device.  For a device with
multiple network interfaces, that kind of sloppy is often too sloppy.

> Here's what I'm shooting for: [...]

   Unless you use a wireless "guest" network on the C7000v2, all devices
on your LAN should be able to communicate with each other, whether
wired or wireless (either radio band).

   However, configuring a device (like, say, a printer) with more than
one interface on the same LAN subnet would be unwise, as would
whimsically enabling/disabling any particular interface.  Your typical
gizmo with multiple interfaces is not expecting to treat them as
redundant paths to the same place, and your typical computer OS is not
expecting one printer to be available at multiple IP addresses.

   All these devices are getting IP addresses on the same subnet
("192.168.0.*", I'd expect), right?  (If not, then you have still more
complications.)

   For a device like a printer, your computers might be happier if the
printer (that is, the one network interface on the printer which is
being used) always had the same IP address.

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual (at least).  Read.  Look for
"Address Reservation".

   If, someday, you decided to use the other interface on the printer,
then I'd guess that you could change that address reservation to apply
to that other interface (with its different MAC address), and the
software on the computers might never notice the difference.