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To: oberman@es.net, wayne.pascoe@realtime.co.uk
Subject: Re: OT: TCP/IP Subnetting
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Date: Sat, 12 May 2001 15:30:20 +1000 (EST)
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>From owner-freebsd-questions@FreeBSD.ORG  Sat May 12 03:31:38 2001
>To: Wayne Pascoe <wayne.pascoe@realtime.co.uk>
>Cc: questions@FreeBSD.ORG
>Subject: Re: OT: TCP/IP Subnetting 
>Date: Fri, 11 May 2001 10:31:27 -0700
>From: "Kevin Oberman" <oberman@es.net>

>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.

Can you expand on this a bit?
I would like to establish a host as a router between our
registered IP #s and an existing 10. based net, via the same
interface...
we have a point ot point link on ng0 (via a frame relay card) and
our internal lan on an fxp interface. i have setup the 
ifconfig to use the 10. address and to real.address as an alias
However it seens that the route mechanism wont allow this as 
there is no forwarding between our 10. net and our real.address net
via the common interface. Is this because it has (of course) the 
same MAC address and the routing s/ware cant cope?

>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


Murray Taylor, Project engineer

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