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Date:      Fri, 25 Sep 1998 12:16:18 -0500
From:      "Jeffrey J. Mountin" <jeff-ml@mountin.net>
To:        ulf@Alameda.net, Bill Vermillion <bill@bilver.magicnet.net>, freebsd-isp@FreeBSD.ORG
Subject:   Re: Routing problem
Message-ID:  <3.0.3.32.19980925121618.00714074@207.227.119.2>
In-Reply-To: <19980924150846.C24890@Alameda.net>
References:  <199809240148.VAA29188@bilver.magicnet.net> <360938BE.3569E424@eaznet.com> <199809240148.VAA29188@bilver.magicnet.net>

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At 03:08 PM 9/24/98 -0700, Ulf Zimmermann wrote:
>On Wed, Sep 23, 1998 at 09:48:10PM -0400, Bill Vermillion wrote:
>> Eddie Fry recently said:
>> > Randal,
>> > 
>> > Ronald says he has 2 class C's so his mask should be 255.255.255.0.
>> 
>> He says he has two class C's but he's using class A addressing.
>> 
>> Shouldn't the netmask really be 254.0.0.0  ?  That way it will
>> supernet the 10.1 and the 10.2  into two parallel blocks out of 
>> address.. 10.1 thru 10.2.   
>
>254 would give you a supernet which includes 10.0.0.0/8 and 11.0.0.0/8.
>
>> 
>> I know you can't use the 1 bit mask in the subnetting a c because
>> it will give a network address and a mask with nothing in between.
>> 
>> Will a 254.0.0.0 set it up so that 10.1.0.0 is the base and 
>> 10.2.255.255 is the broadcast.
>
>To do that, the netmask would be 255.252.0.0, but that would include
>10.0.0.0/16, 10.1.0.0/16, 10.2.0.0/16 and 10.3.0.0/16, so the broadcast
>would be 10.3.255.255

But isn't 10.0.0.0/255.254.0.0 a valid netmask?  It would give 10.0.0.0/16 and 10.1.0.0/16, which wouldn't work for the posted is doing ie routing between the 2 networks.

It certainly isn't a CIDR mask, but should be valid for supernets.


Jeff Mountin - Unix Systems TCP/IP networking
jeff@mountin.net

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