Oracle VM VirtualBox。 Network bridging problem.

First of all, the network card of your friend's computer must be powered on. Secondly, you can use Nat or bind the network card connected to the network. Then, if you connect through a route or switch, you must modify the network card in the virtual machine, and the modification depends on whether you set it dynamically or statically at the routing end. If it is dynamic, it can automatically obtain DHCP; if it is static, it can write its own IP, subnet mask, gateway and DNS.