New Ubuntu Instance Gets Error "No route to host" For Hosts On External Networks

A newly created Ubuntu Instance running in Oracle Cloud Infrastructure (OCI) encounters an error "No route to host" whenever it tries to connect to HTTP and HTTPS services running on hosts on external networks, such as in the following example:

ubuntu@instance:~$ wget http://****.****.****.****

Connecting to ****.****.****.****:80... failed: No route to host.

This error is caused because, in addition to the Egress/Ingress rules allowing the Ubuntu instance to access external hosts needing to be configured within the OCI User Interface, the Ubuntu Instance also needs it's own firewall rules to be setup within its operating system.