e.g. preparing multiple virtual machines in local network

Hostnames: VM node-A, VM node-B, VM node-C

Adapter 1: Host-only Adapter (VirtualBox-Host-Only Ethernet Adapter)
Type -> Paravirtualized network adapter (virtio-net) - Deny Mode

Adapter 2: Bridged Adapter (Intel Ethernet Connection)
Type -> Paravirtualized network adapter (virtio-net) - Deny Mode

Test
Try to connect one of VMs such as "node-A" by SSH

How to connect into local VM via SSH?

* Set a new Port Forwarding Rule in Network Settings

Step 1: Settings -> Network -> Adapter 1 -> Advanced -> Adapter Type -> "Paravirtualized network adapter (virtio-net)" -> OK

Step 2: Settings -> Network -> Adapter 1 -> Advanced -> Keep it as "NAT" -> Click "Port Forwarding" -> Define a Rule -> OK
e.g.
Name Protocol Host Port Guest Port
SSH TCP      1022 22

SSH Connection Host/Port Settings:
Host: 127.0.0.1
Port: 1022

How to see both Oracle VM Virtual Box 32bit/64bit options?

e.g. If there are only 32 bit Linux distro in the OS list, you should enable virtualization support in BIOS

* BIOS -> CMOS Setup Utility -> Virtualization Technology -> [Enabled]