Canonical domain names for private LANs?

[Philipp Lehman <lehman@gmx.net>]

I have a small home LAN consisting of three machines, one of which
connects the LAN to my ISP over a dial-up connection. I was wondering
what domain name to use for the LAN. What I have in mind is something
similar to the IP address space(s) reserved for private use (such as
192.168.*.*)

While searching the web I found a pointer to RFC 2606 which lists four
top level domains reserved for private use and testing (.test,
.example, .invalid, and .localhost). I seems to me that ".invalid"
would be suitable for a dial-up machine with a dynamic IP address. Is
this actually the canonical way?

And the (Debian specific ;) question is: is anybody using host names
like "<hostname>.localnet.invalid" on a Debian machine? Will this work
with standard Debian tools such as Exim, i.e. can I use it just like
any other (unregistered) domain name or should I expect certain apps
to actually treat it as invalid (and bouce mail, for example)? -TIA

-- 
Philipp Lehman <lehman@gmx.net>