How do I prevent DHCP'd interfaces from coming up automatically on boot?

["Joe Emenaker" <joe@emenaker.com>]

I've got a built-in ethernet jack on my laptop. Being a laptop... this jack
is often not plugged into anything (aka: I don't want it coming up
automatically on boot). However, being a laptop, when it *is* plugged in, it
gets plugged in at a variety of places (aka: I need DHCP).

The problem is that, if I set up my /etc/network/interfaces like so:

      auto lo
      iface lo inet loopback

      iface eth0 inet dhcp

then Debian seems to try to bring up eth0 *anyway*. /etc/network/interfaces
claims that I can use a "noauto <interface>" directive, but I get an error
message on the console (about a syntax error in /etc/network/interfaces, of
course) at boot time when I try that.

Am I missing something here? Is it the prescribed behavior for the "dhcp"
directive to imply "auto"?

- Joe