Cable modem network setup recommendations

[Rune Mossige <r.mossige@sensewave.com>]

Hello,

I am about to connect a small community-operated, non-profit Cable TV company
to the internet, via a Cabletron SSR2000, ARRIS 1000 CMTS and Toshiba PCX2500
cable modems.

This is something that I have never done before, and would therefore ask for
advise on how to design, configure, and run this small network.

The initial roll-out will be about 40 households, expected to grow to about
150 within the next 12 months.

The logical network looks like this:

ISP -> Router -> OpenBSD -> CMTS -> Cable Modem -> PC

The physical cable modem and the CMTS is on a private network, 172.16.0.0/16,
and the CMTS forwards DHCP requests from the cable modems onto a fixed
address, 172.16.255.254, which is one interface on the OpenBSD box. Now, the
modems gets a config file, and one or more official IP-addresses for the PC's
to use....In the future, we hope to be able to serve a range of RFC1918
addresses to some selected PC's, and then have the OpenBSD box NAT them.

Does this make any sense, or is more details required? If so, please ask.

My first thought was to set up the OpenBSD box with bridging, giving an
official IP-address to one interface, and leave the other un-named, and bridge
between these two logical subnets, which happens to be on the same physical
network. But I could not get that to work.

Right now, the OpenBSD box have both interfaces assigned, one on the official
net, and one on the 172.16 net.

So, I am open for suggestions, and recommendations for what to do.

-- 
(-: Hiroshima 45, Tsjernobyl 86, Windows 95 :-)
Rune Mossige, Brekkeveien 19, N-4353 Klepp Stasjon, NORWAY
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