Cisco unnumbered loopback

Cisco allows you to assign an IP address to the loop back and use that with the IP unknumbered interfaces. The advantage is that the loopback never goes down. I don't think we can use it since we'd need an IP address for the loopback and for the ethernet (you can only use IP un-numbered on serial links) and we'd need to publish the route to the loopback via OSPF as well. See these pages 1 2 for more info.