There's a whole bunch of software out there that makes certain
assumptions about allowable ranges. That is, they've been compiled with
a header that defines ..

Of course correct. It really depends on the vendor / software / versions in an environment. A lot of vendors removed that years ago, because frankly a lot of large networks have been using 240/4 as pseudo RFC1918 for years. Others have worked with smaller vendors and open source projects to do the same.

It's consistently a topic in the debates about 240/4 reclassification.

On Wed, Jan 10, 2024 at 10:45 AM Michael Butler <imb@protected-networks.net> wrote:

On 1/10/24 10:12, Tom Beecher wrote:
> Karim-
>
> Please be cautious about this advice, and understand the full context.
>
> 240/4 is still classified as RESERVED space. While you would certainly
> be able to use it on internal networks if your equipment supports it,
> you cannot use it as publicly routable space. There have been many
> proposals over the years to reclassify 240/4, but that has not happened,
> and is unlikely to at any point in the foreseeable future.

While you may be able to get packets from point A to B in a private
setting, using them might also be .. a challenge.

There's a whole bunch of software out there that makes certain
assumptions about allowable ranges. That is, they've been compiled with
a header that defines ..

#define IN_BADCLASS(i) (((in_addr_t)(i) & 0xf0000000) == 0xf0000000)

Michael