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    SubjectRe: all zeroes/all ones used in host IP's...
    On Fri, Jan 28, 2000 at 03:42:16PM -0700, Michael Loftis wrote:
    > 255 is forbidden because it's the broadcast address. As to 0 being
    > forbidden, uhm.. I think that's only as the last octet in a host
    > sequence. Why? My nameserver is at 209.161.0.2 and 209.161.0.3

    No.... 255 is illegal only for a /24. 255.255 is illegal for
    a /16. 0.255 is perfectly legal for a /20 or bigger. 0.127 is illegal
    for a /25.

    > Whatever 1123 says .0 seems to have been accepted in a network mask
    > sense, but I would doubt that as a last octet of a host it would not
    > work.

    It will work just fine if the network mask is bigger than a /24.
    130.205.1.0 is perfectly fine if it's a /16 but illegal if it's masked down
    to a /24.

    Stop thinking in octets. This stuff is binary.

    > IE
    > 209.161.0.0/32 (Host) is illegal
    > 209.161.0.1/32 (Host) is legal
    > 209.161.0.0/24 (Network) is legal

    > --
    > Michael Loftis
    > ICQ: 15648280 AIM: DyJailBait
    > Funny quip of the moment just happens to be....
    > Linux is like a tent:
    > no gates, no windows, and an Apache inside!
    >
    >
    > -----Original Message-----
    > From: "Mike A. Harris" <mharris@meteng.on.ca>
    > Date: Fri, 28 Jan 2000 12:44:51 -0500 (EST)
    > Subject: all zeroes/all ones used in host IP's...
    >
    > > On another mailing list I'm on there is a small discussion about
    > > using "0's" in IP addresses. Nobody could categorically say
    > > wether or not they are allowed or not including myself, so I
    > > hunted down RFC 1123, and found the relevant section.
    > >
    > > Here it is:
    > >
    > > 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).
    > > This implies that each of these fields will be at least
    > > two
    > > bits long.
    > >
    > > Now I interpreted that as meaning that none of the octets in an
    > > IP address could be 0 or "-1" in either the network/subnet or
    > > host portions of a valid host IP. The definition of "-1" is "all
    > > ones" in the host or network/subnet portion.
    > >
    > > I interpret the above as meaning that it is not legal to have a
    > > network like this:
    > >
    > > 192.168.0.0/24 or 23.0.0.0/24
    > >
    > > with hosts 192.168.0.1 through 192.168.0.254 or with hosts
    > > 23.0.0.1 through 23.0.0.254.
    > >
    > > The first zero makes it illegal no? Could someone in the know
    > > please clarify this as it has been bugging me for some time and
    > > nobody else seems to be able to say with 100% certainty what the
    > > proper rule is. Also, would a network like:
    > >
    > > 142.255.255.0/24 be illegal?
    > >
    > > Someone has suggested that my interpretation is wrong, and if
    > > that is indeed so, I'd like to know the proper interpretation and
    > > share it with everyone.
    > >
    > > I looked through some of the kernel source and couldn't find any
    > > special handling of such addresses.
    > >
    > > Thanks very much in advance.
    > > Take care!
    > > TTYL
    > >
    > > --
    > > Mike A. Harris Linux advocate
    > > Computer Consultant GNU advocate
    > > Capslock Consulting Open Source advocate
    > >
    > > Join the FreeMWare project - the goal to produce a FREE program in
    > > which you can run Windows 95/98/NT, and other operating systems.
    > >
    > > http://www.freemware.org
    > >
    > >
    > > -
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    > > Please read the FAQ at http://www.tux.org/lkml/
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    >
    >
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    --
    Michael H. Warfield | (770) 985-6132 | mhw@WittsEnd.com
    (The Mad Wizard) | (770) 331-2437 | http://www.wittsend.com/mhw/
    NIC whois: MHW9 | An optimist believes we live in the best of all
    PGP Key: 0xDF1DD471 | possible worlds. A pessimist is sure of it!


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