[ubuntu] Virtualbox server not accessable from host

I've installed Ubuntu lamp server on a Virtualbox. The host is Ubuntu 12.04. The virtualbox server has access to internet and can ping router and host IP while getting a DHCP IP, although subnet mask is weird.
host:
10.0.0.21 255.255.0.0 gateway 10.0.0.2

virtualbox server from dhcp:
10.0.2.15 255.255.255.0 10.0.0.2

As I said, although the subnet mask is not the same, access and pinging is fine. Network settings are set on NAT.

BUT, when I try to access the lamp server from the host (http://10.0.2.15), I do not get access (it works from within the virtualbox, so setup and config is working).

I tried to change virtualbox server's IP to static (10.0.0.1 255.255.0.0 gateway 10.0.0.2) with NO access to and from nowhere. No router, no host, or the other way round.

Can someone tell me what I should do to get the virtualbox server (10.0.2.15) web accessable from host (10.0.0.21)? I need to configure a web app on the virtualbox server from the host.