vboxnet0 internet NAT

To get network address translation (internet) on the hostonly network of a Linux host?
Assuming default configuration, do the following on the host:
1. Enable port forwarding
sysctl -w 'net.ipv4.ip_forward=1'
2. Enable masquerading of the hostonly network
iptables -t nat -A POSTROUTING -s 192.168.56.0/24 ! -d 192.168.56.0/24 ! -d 127.0.0.0/8 -j MASQUERADE
3. Write down your DNS server IP's and supply them to the guests.
4. Tell guests that 192.168.56.1 is their default gateway.
Now, you should have internet in the hostonly network.
This is one-time change, and will reset after reboot.