I developed IP-over-OSPF for a networking class four years ago. It continues with the great tradition of IP-over-<FOO> demos, many of which can be found on HN [1].
One neat thing about this version is that it makes it possible for two machines to communicate over IP, _before the network is even done being configured_! Indeed, two machines could be communicating with IP-over-OSPF even before OSPF is done setting up the routing tables.
But the real "aha!" comes from the realization that IP-over-OSPF should really be called tap-over-OSPF or Ethernet-over-OSPF: it gives you an Ethernet link built on top of the OSPF protocol. All the machines connected to the same OSPF "network" (known as an autonomous domain) are conceptually on the same link.
But what if you wanted two machines on _different autonomous domains_ to communicate? If you have an OSPF router present on both autonomous domains, this machine could be forwarding between one "link" to the other. And how do you setup IP addresses across these links then?
You may need to run OSPF over IP-over-OSPF... and you know what you could try next!
Useful? Probably only for a BOFH in need of a quick "network infrastructure upgrade" before the intern takes over.
[1]: https://hn.algolia.com/?query=ip%20over
