There are many times that I need to launch a virtual Linux server to test something. If no Ubuntu specific feature is needed, I often use Alpine Linux for the virtual machine, for its lightness.
When I run a Linux VM, I always need to SSH to it, so in VirtualBox, I need to select "Bridge Adapter" as network adapter. Things just work fine if the guest machine is Ubuntu. But the first time setup for Alpine Linux (as guest machine), it doesn't work and the virtual machine cannot talk DHCP. In that case, you have to do one more step. Under Network Adapter > Advanced, look for "Adapter Type" and change it to "Paravirtualized Network (virtio-net)".
For more info about VirtIO, you can read here: https://www.ibm.com/developerworks/library/l-virtio/