class-C designation

[Marc Haber]

On Fri, Oct 05, 2007 at 06:01:31PM -0700, Jim Pazarena wrote:
> I have just been assigned a /23 network.
> I am used to /24 and referring to it as a "class-C".

Which is incorrect if the first octet is below 192.

Please stop thinking and talking classfully, classful IP addressing
has become irrelevant more than ten years ago and classful thinking is
more a burden and source of confusion these days.

> Is there a name which may refer to a /23 network? Or must I simply
> refer to it a "two back-to-back class-C's" ?

How about "slash twenty-three"? And, please, refer to the smaller
network as "slash twenty-four".

> Second question. In a /23, is it permissible for me to use the inner .255/.0 numbers?

Yes, of course. There are some broken implementations around that
refuse addressing these, but these implementations are broken.
Theoretically, you could even use the first address in your /23.

> The telco told me I could not use them, but it doesn't make sense if indeed they
> have routed me a /23.

They need a clue bat or just want to make sure.

Greetings
Marc

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