[anderbubble]

That's the thing: people don't put their HPC clusters on the public Internet; so an internal IPv4 network just keeps being fine.

[ale42]

True, but on the other hand it might be that all private use blocks are already in use (10.0.0.0/8 is totally in use in our internal LAN), so if I want the nodes to reach those private IPs, I can't assign the same block. And we do have services on IPv6.