Geek pop quiz, virtual machine networking edition! (SOLVED)

Ubuntu server running VirtualBox has globally-visible routable static IPs N->N+5 available to it. It is using IP N itself, and has lovely internet access via IP Q (on a completely different subnet, same ethernet card)

A virtual machine is created with Bridged networking to eth0, using IP N+1.

It is accessable from the internet via RDP to the *host server* because VirtualBox does that, and that means I'm connecting to the host, not the VM.
It is accessable via ping and SSH *from* the host server, via IP.
It can ping and ssh *to* the host server, via IP.

It can't go further than the host server and nothing from the outside can get to it.

"route -n" on the host and the VM produce sensible-looking results that perfectly match a working identical configuration (with different IPs, of course)

This is a fresh install, on a brand new machine.
Telling the host server that *it* is IP N+1 (or 2, or 3, or whatever) results in perfectly good network access to and from those IPs.

Any ideas?

EDIT: The problem is definitely routing of some sort. The host happily bounces out via IP Q, traceroute from the outside to N goes in to N via Q no problem - but the virtual machine can't ping Q. So when then VM is connecting to the outside world, it goes to N (it's gateway), then the host doesn't pass that along to Q and out to the intertubes.

EDIT2: IPv4 Packet Forwarding in /etc/sysctl.conf FTW.

Fixed it myself. I love you guys, sometimes just ASKING the question is enough to jog me through figuring out where to look.

Purest, vilest heresy.

Oxford's manual of style disavows the Oxford Comma.

This, as all right-thinking people understand, is absurd, wrong, and evil. When making a comma-delimited list, one delimits the list items with commas. Period.

(So to speak)

via kafziel

PONY

So, I have a Google+ invite.

Does anyone know what it *is*?

Is like Buzz, the tool where nobody knows what it's good for or what you can do with it, or like Wave, where nobody knows what it's good for or what you can do with it? Or is it more like facebook, where it's useless crap that does nothing and EVERYONE knows it?

I mean, seriously. What is Google+ and why would I possibly want it?

EDIT: If you uncheck the "let Google use your personal information to spam you" checkbox, it won't let you sign up at all. FUCK. THAT.