Messages in this thread | | | Date | Fri, 28 Jan 2000 18:46:13 -0500 | From | "Michael H. Warfield" <> | Subject | Re: all zeroes/all ones used in host IP's... |
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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 > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe > > linux-kernel" in > > the body of a message to majordomo@vger.rutgers.edu > > Please read the FAQ at http://www.tux.org/lkml/ > > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.tux.org/lkml/
-- 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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