[24976] in North American Network Operators' Group
Re: The Mathematical Reality of IP Addressin in IPv4...
daemon@ATHENA.MIT.EDU (Eric Germann)
Thu Aug 26 17:59:43 1999
Date: Thu, 26 Aug 1999 17:45:39 -0400
To: bmanning@vacation.karoshi.com
From: Eric Germann <ekgermann@cctec.com>
Cc: nanog@merit.edu
In-Reply-To: <199908261743.KAA07559@vacation.karoshi.com>
Errors-To: owner-nanog-outgoing@merit.edu
At 10:43 AM 8/26/99 -0700, bmanning@vacation.karoshi.com wrote:
>
>> What this proposal appears to be proposing is to permit NON-CONTIGUOUS
>> netmasks such as:
>>
>> 255.128.127.0
>>
>> Or, in binary:
>>
>> 1111111111 10000000 01111111 00000000
>>
>> Thus, the network number would actually consist of all 8 bits of octet
>> one, the first bit of octet two, the last 7 bits of octet 3 and none of
>> octed four.
>>
>
>Non-contigious masks were allowed up until the CIDR era... :)
>
>--bill
>
As an exercise in insanity, when I teach my TCP/IP course, I use the
following example
206.183.244.0 / 255.255.255.170
and ask the students to find the subnet address, first usable node, last
usable node and broadcast address for each subnet. Takes them about three
hours and then they appreciate the recommendation that all subnet bits be
contiguous. What it does do very well is hammer home how these things
actually work in terms of varying the host bits and network bits :)
eric
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