We now have our Banana Pi up and running with a clean installation of Bananian Linux. To get it working as a gateway, we need to do 3 things:

• set up a DHCP server, so that computers can join the network.
• set up a DNS server, so that domain names can be resolved.
• set up NAT, so that internet requests can be made on behalf of other computers on the network.

Once you've set up these 3 things, you will have a basic gateway up and running, and other computers on the internal network should have internet access.

The diagram below shows how it all fits together:

• When a new computer^[1]That has been configured to use DHCP. joins the network, it will contact the DHCP server running on the bPi to get an IP address. As part of this assignment, the bPi will tell the new computer that it also handles DNS requests, as well as any other internet activity.
• If someone wants to go to a web site, they will ask the DNS server to look-up the domain name, to get the web site's IP address.
• Finally, NAT ensures that internet requests go out, and replies come back in, transparently.