Randy Bush <randy@psg.com> wrote:
as a measurement kinda person, i wonder if anyone has looked at how much progress has been made on getting hard coded dependencies on D, E, 127, ... out of the firmware in all networked devices.
The drafts each have an Implementation Status section that describes what we know. The authors would be happy to receive updates for any of that information. 240/4 is widespread everywhere except in Microsoft products. It works so reliably that both Google and Amazon appear to be bootlegging it on their internal networks. Google even advises customers to use it: https://cloud.google.com/vpc/docs/vpc#valid-ranges 0/8, and the lowest address per subnet, have interoperable implementations that don't cause problems with legacy equipment, but they are not widely deployed. 0/8 has a few years in Linux & Android kernels and distros. Lowest address is in the most recent Linux and FreeBSD kernels, but not yet in any OS distros. In particular, OpenWRT doesn't implement it yet, which could easily be a fast path to a free extra IP address for anyone who has a compatible home router and a globally routed small network like a /29. We used RIPE Atlas to test the reachability of many addresses that end in .0 and .0.0, and they were reachable from all but one probe that we tried. Amazon offers https://ec2-reachability.amazonaws.com/ for this purpose; try it on your own network! Some embedded TCP stacks treat 127/8 as unicast (simply because they don't special-case much of anything), but otherwise we don't know of any current OS distributions that implement unicast for 127/8. The Linux kernel has long had a non-default "route_localnet" option offering similar but more problematic behavior. I would be happy to fund or run a project that would announce small global routes in each of these ranges, and do some network probing, to actually measure how well they work on the real Internet. We are working with RIPE Atlas already to enable this. I thought it would be prudent to propose the changes in detail to IETF, before "bogus" routes showed up in BGP and the screaming on the NANOG list started. :-/ John