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

[Michael Loftis]

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 

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.

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 en 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
> 
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> 
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