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Groups > comp.os.linux.networking > #1604

Re: Dealing with a network knowledge troll!

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On 24 Aug 2012, in the Usenet newsgroup comp.os.linux.networking, in article
<slrnk3eajg.ph6.grahn+nntp@frailea.sa.invalid>, Jorgen Grahn wrote:

>Mike Lovell wrote:

>> I've got a guy who claims these:

>>       10.255.255.81/24
>>       192.168.255.81/24

Those are RFC1918 (private) addresses.  Tell the idiot to set up a
couple of boxes in those ranges and try it himself.

>> Are invalid unicast IP's, because any IP with a "255" in it
>> *anywhere* is reserved for being a broadcast IP.

  1122 Requirements for Internet Hosts - Communication Layers. R.
       Braden, Ed.. October 1989. (Format: TXT=295992 bytes) (Updates
       RFC0793) (Updated by RFC1349, RFC4379, RFC5884, RFC6093,
       RFC6298, RFC6633) (Also STD0003) (Status: STANDARD)

RFC1122 section 3.2.1.3 is poorly written, but sub section '(d)' and
'(e)' limit it to the last address in a network/subnet (the -1) only.

>If you really have found it stated in the RFCs and the RFCs are not
>obsoleted by later ones, of course you are right and don't have to
>ask around.

RFC1878

  1878 Variable Length Subnet Table For IPv4. T. Pummill, B. Manning.
       December 1995. (Format: TXT=19414 bytes) (Obsoletes RFC1860)
      (Status: HISTORIC)

>(Why stop at octets 1--3, by the way?  Surely a.b.c.255 can be a
>valid unicast address too?)

Depends on the network mask, but sure.  A facility I worked at for five
years used a 255.255.252.0 (0xff ff fc 00) mask, so three out of four
x.y.z.255 addresses were "normal" host addresses (only a broadcast
where 'z' divided evenly by 4).  Thus,

    198.18.4.0     network address
    198.18.4.1     thru
    198.18.7.254   are host addresses
    198.18.7.255   the ONLY broadcast address of the lot

That meant 198.18.4.255, 198.18.5.255  and 198.18.6.255 were hosts.

        Old guy

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Thread

Dealing with a network knowledge troll! Mike Lovell <dev.null@b0h0.com> - 2012-08-23 22:07 -0500
  Re: Dealing with a network knowledge troll! David Brown <david@westcontrol.removethisbit.com> - 2012-08-24 09:05 +0200
  Re: Dealing with a network knowledge troll! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-08-24 07:17 +0000
    Re: Dealing with a network knowledge troll! Moe Trin <ibuprofin@painkiller.example.tld.invalid> - 2012-08-24 10:29 -0500
    Re: Dealing with a network knowledge troll! Mike Lovell <dev.null@b0h0.com> - 2012-08-24 10:53 -0500
      Re: Dealing with a network knowledge troll! "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2012-08-24 14:02 -0400
      Re: Dealing with a network knowledge troll! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-08-24 20:21 +0000
  Re: Dealing with a network knowledge troll! Richard Kettlewell <rjk@greenend.org.uk> - 2012-08-24 09:07 +0100
  Re: Dealing with a network knowledge troll! telsar <noone@nowhere.com> - 2012-08-24 12:09 -0500
    Re: Dealing with a network knowledge troll! Moe Trin <ibuprofin@painkiller.example.tld.invalid> - 2012-08-24 14:29 -0500
      Re: Dealing with a network knowledge troll! telsar <noone@nowhere.com> - 2012-08-24 15:58 -0500
        Re: Dealing with a network knowledge troll! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-08-24 22:23 +0000
          Re: Dealing with a network knowledge troll! telsar <noone@nowhere.com> - 2012-08-25 12:40 -0500
    Re: Dealing with a network knowledge troll! Richard Kettlewell <rjk@greenend.org.uk> - 2012-08-25 09:38 +0100
      Re: Dealing with a network knowledge troll! telsar <noone@nowhere.com> - 2012-08-25 12:35 -0500

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