From owner-freebsd-questions  Fri May 11 12:33:59 2001
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Date: Fri, 11 May 2001 12:33:50 -0700 (PDT)
From: Rick Duvall <maillist@coastsight.com>
To: Kevin Oberman <oberman@es.net>
Cc: Wayne Pascoe <wayne.pascoe@realtime.co.uk>, questions@FreeBSD.ORG
Subject: Re: OT: TCP/IP Subnetting 
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I like to use a spreadsheet to keep track of my IP addresses.  Use 1
column for each /24, then count the number of cells down and put the
network and broadcast addresses where they go and color code them.  Color
with a different color the used subnets, then bold the used IP addresses
and label what each one goes to.  It is MUCH easier to keep track what is
where, and so forth.

Sincerely,

Rick Duvall

On Fri, 11 May 2001, Kevin Oberman wrote:

> Wayne,
> 
> There are better possibilities.
> 
> Break up the /25 as follows:
> Size   Addresses       Start Address    Net Mask
> /26   62 addresses     128.1.1.128	255.255.255.192
> /27   30 addresses     128.1.1.192	255.255.255.224
> /28   14 addresses     128.1.1.224      255.255.255.240
> /29    6 addresses     128.1.1.240      255.255.255.248
> 
> You may move the blocks around, but be careful calculating the
> addresses!
> 
> Use the /29 for your 4 machine space. Use the other spaces for the
> rest of the systems, starting with the largest (/26). You can work
> communication by either setting up a system as a router between the
> address spaces or, more cleanly, you can set up appropriate routing
> table entries on each system with routes to the local network for each
> subnet that is used in the LAN.
> 
> This means pointing 128.1.1.128, 128.1.1.192 and 128.1.1.224 at the
> local link. See the route(8) and netstat(1) man pages for more hints
> on how this can be done. Note that route(8) in FreeBSD does support
> CIDR add/len notation to make this easier.
> 
> It has a major downside in requiring the configuration be loaded on
> EVERY system.
> 
> While this looks ugly, it's how the Internet works and all providers
> do this routinely, although it's far easier to configure on a Cisco or
> Juniper than on a FreeBSD host.
> 
> R. Kevin Oberman, Network Engineer
> Energy Sciences Network (ESnet)
> Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
> E-mail: oberman@es.net			Phone: +1 510 486-8634
> 
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