Re: LAN IP addresses

Moe Trin a écrit :
Pascal Hambourg wrote:
Moe Trin a écrit :

But then, a lot of people misinterpret RFC1122 Section 3.2.1.3 on
page 31 (third paragraph below (g)) as prohibiting a zero (or -1
which they don't understand) in any host part.

Hey, I interpret this paragraph this way too ! :-o
I quote it for completeness :

IP addresses are not permitted to have the value 0 or -1 for
any of the <Host-number>, <Network-number>, or <Subnet-
number> fields (except in the special cases listed above).

To me it clearly means that the host number part of a unicast host
address cannot be 0. What I am reading wrong ?

What is the "host number part"?

It is the right-most part of the IP address which has the corresponding bits in the netmask set to 0 ass assumed in the RFC. Isn't it what you meant by "host part" ?

Most people wrongly assume that this
refers to the right-most octet only,

They're wrong. This is true only for /24.

Oh, and you may also want to notice the "<Subnet-number>" mentioned
above (also mentioned in RFC1812 and the various 'Assigned Numbers"
RFCs like RFC1700), and then look at RFC3330. It was common with some
operating systems that the lowest and highest _subnet_ were considered
unusable.

I knew about this. Actually I tend to consider that the subnet number is deprecated since the advent of CIDR. An IP address contains a prefix and a host number. Whether the prefix is the result of subnetting does not matter to me, and I believe it should not matter to any network equipement either.
.

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