o1bigtenor via Dng <dng@???> writes:
> On Sun, Jun 4, 2023 at 6:05 PM Antony Stone
> <Antony.Stone@???> wrote:

[...]

>> At this point it's useful to note that two addresses "disappear" from every
>> network range and cannot be assigned to machines on the network - the first
>> address and the last address.

[...]

> I seem to remember that 0.0, 1.1 and 255.255 were reserved from any group.
> not allowed to use the 0.0 and the 255.255 as you mention and that 1.1 is the
> router's address.

The two special cases are 'host bits all zero' and 'host bits all
one'. Both are reserved for IP-directed broadcasts (a feature nobody
uses anymore today), the first reportedly because 4.2BSD used it for
this, the second because it got later standardized by the IETF. There's
nothing special about the first non-reserved address, eg,
192.168.1.1. It's commonly used for default gateway addresses. But
there's also the other convention to use the last address for that, eg,
192.168.1.254, and both are just informal conventions.