Nighthawk R6400 - Redirect outgoing IP address

> [...] I was hoping that a typical router would keep a small domain
> name table within its local memory. [...]

   Some might.  Even some Netgear models might.  I've never seen a
Netgear model which allows the user to fiddle with anything of that
sort.  Hence the suggestion of a local DNS server (or "hosts" file),
with which you _can_ fiddle.  (A Raspberry Pi, for example.)

   This kind of redirection stuff is not impossible, but getting a
consumer-grade Netgear router to do it might be tough.

   The DNS processing in a typical Netgear router does intercept names
like "routerlogin.net", and deals with them internally, so it's not as
if the whole concept is foreign, but it's not intended to be
user-configurable.  (And I know approximately nothing about the
details.)

   If your R6400[vX?] allows you to enable Telnet access into it, then
you might be able to find a way poke something into it to get the
desired effect, but something like a firmware update, or even a restart,
might clean out any such modification.  (And Netgear has crippled that
(undocumented) feature in recent R7000 firmware, too, so relying on it
carries its own dangers.)  Everything's complicated.