While working on how to set up an out-of-band communication network between several providers, a question about whose IP addresses to use came up. The intent is to provide an out-of-band management network allowing member providers to exchange management information and alerts even if the main Internet is severely congested by malicious traffic. Because this isn't supposed to be connected to the Internet, its not necessary to use IANA/ARIN/RIPE/APNIC assigned IP address blocks. Several providers use private addresses on their out-of-band management networks. I would prefer to use globally unique IP addresses between providers to avoid conflicts with the RFC1918 private addresses already in use in provider's networks, and if the addresses accidently leak. Other than exchange points, are there any other cases of unique IP addresses being allocated for multi-provider purposes?