[ubuntu] Ubuntu Server Network connection Virtual Box

Hello,

I am beginner on Ubuntu server and linux in general.

I would like to connect a virtual ubuntu server to both a virtual lan network as well as the internet.

For this I've enable two networks cards on virtual box for this particular virtual machine.

Unfortunately my internet connection works only when I set just one card (the first) in NAT.

My question: how to define the network card where the internet trafic is suposed to come from ? Which option enable or modify in which file ?

Thank you in advance :)