Re: 202401100645.AYC Re: IPv4 address block

[Tom Beecher <beecher () beecher cc>]

> 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