Great Circle Associates Firewalls
(January 1995)
 

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Subject: Re: subnetting
From: lavondes @ tidtest . total . fr (Michel Lavondes)
Date: Mon, 30 Jan 95 12:00:06 GMT
To: hobbit @ bronze . lcs . mit . edu (*Hobbit*)
Cc: firewalls @ greatcircle . com (fw)
In-reply-to: <199501300638 . BAA17741 @ bronze . lcs . mit . edu>; from "*Hobbit*" at Jan 30, 95 1:38 am
Reply-to: lavondes @ tidtest . total . fr

*Hobbit* wrote :
> 
> Subnetting with 255.255.255.128 works fine here.  Which RFC says you
> need to use sets of two bits?  I looked around a bit and didn't find it --
> 

If you use that mask with a class A or B address, fine. If you use it with
a class C address, the only subnet #s you get are either all-zeroes or all-ones,
and AFAIR both are reserved (all-zeros for the "local" subnet and all-ones for
all subnets.) This, I think, is stated in one of the RFCs on subnetting.
Notwithstanding, some boxes allow use of an all-zeroes subnet.

HTH
-- 
Michel Lavondes
E-Mail : lavondes @
 tidtest .
 total .
 fr
         lavondes%tidtest .
 total .
 fr @
 pegase .
 total .
 fr (if previous addr rejected)
Tel : +33-1-4135-4198
Fax : +33-1-4135-4189


References:
  • subnetting
    From: hobbit @ bronze . lcs . mit . edu (*Hobbit*)
Indexed By Date Previous: Re: How many firewalls & what IS one?
From: "Johnson-Bryden, Ian" <IJB @ saicuk . co . uk>
Next: ftp and news through TIS firewall with Netscape WWW browser
From: a . smith . kainos @ oasis . icl . co . uk
Indexed By Thread Previous: subnetting
From: hobbit @ bronze . lcs . mit . edu (*Hobbit*)
Next: Re: subnetting
From: Brian Utterback <blu @ mc . com>

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