I think you're close! If you can ping 127.0.0.1 then Miami probably needs a proper IP address that is unused on your network, a netmask, a default gateway, and a DNS server address.
If you have another computer on the same network segment, try getting the details from there.
Miami does not support DHCP as far as I can tell so it can't get a network address automatically like most modern computers. So you have to static-route it and set a reservation in the local router so nothing else grabs the Amiga's address.
The alternative is to buy Roadshow as a TCP stack. It's still being developed commercially and has DHCP support so you can let your router do the configuration for you!
