all zeroes/all ones used in host IP's...

[Magnus Danielson]

From: hpa en transmeta.com (H. Peter Anvin)
Subject: Re: all zeroes/all ones used in host IP's...
Date: 28 Jan 2000 11:55:20 -0800

> You are, indeed, completely wrong.  There rules are that neither the
> *entire* network portion or the *entire* host portion of the address
> can be all 0 or all 1.

No, he is correct if you go by RFC 1122. However, if you are running CIDR you
are right. It seems most posts on this topic actually misses the pre/post CIDR
conditions and you really have to read the full section of RFC 1122 and think
of what class the address at hand has in order to fully interprent the
paragraph that he quoted correctly.

Today should everyone run classless and thus will the special case of the
subnet number not apply anymore. However, the host number part of the address
will obey the rules of RFC 1122 even if we nowdays move the subnet/host bit
boundary.

By looking in the latest "Internet Architecture Board Standards Track" RFC,
namely RFC 2400 you will find that the CIDR architecture RFC (1518) is stuck
at Proposed Standard Protocols level in elective status where it has been for
many years and been usefull in the meanwhile. The latest RFC-index reveals the
same level. So, you can't say that CIDR is standard, but it is on the standard
track and we should use it, so in this sence is Peter almost correct ;)

Cheers,
Magnus

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