[lug] cable modem in the Tech Center
archer at meer.net
Mon Mar 6 09:42:37 MST 2000
----- Original Message -----
From: "Michael J. Hammel" <mjhammel at graphics-muse.org>
> It looks like I'm going to be getting a cable modem. I don't know
> about these other than they work on a shared local network design, ie
> are a group of people in my area that technically have access to my box
> the time. So, I need to know a few things.
> 1. Who provides such access?
Your cable company. They will act as both transport provider
and ISP. This is not a good thing. Oh, and the shared bandwidth
effect is real. If you remember the bad old days of 200 workstations
on a single thicknet segment, you know what cable modem is like.
> 2. What are the costs?
Not too bad. Again, it depend on the provider.
> 3. What equipment do I need? I have thinnet at home (yes, 10 year old 8
> bit 3Com and WD cards running on thinnet coaxial cable). Any problems
> with hooking that with the cable hookup?
AFAIK, "cable modems" are usually designed to be hooked up to a single
machine, so you would need to use a (linux) box as a gateway. They usually
do not have NAT (and certainly not MASQ), so you'll need to gateway
anyway. Also, check with your provider: they will probably throw in a
cheap 10baseT card and null-ether cable, which you should take on general
> 4. What security precautions should I take? Should I get a firewall box?
When you get a cable modem, you are effectively on the internet full
time, so you need to take all available precautions. This includes a
real passwords on your internal accounts, and regular audits of your
machines. You will probably have script kiddies infesting your network
within minutes of hooking up (I know I did!). So far, I haven't noticed
these guys to do a lot of harm. I'm sure they are hiding in the cracks,
I'm currently running an insufficient filtering firewall/gateway on RH6.0
talking to a Cisco 625(?) DSL router. I use MASQ to hide the other
machines behind the "firewall." This is far from a perfect setup, but
if you run filtering and proxies on the firewall (which I haven't bothered
with yet) in addition to MASQ you be mostly ok.
Slow Pentiums and even a fast 486 will work for your firewall/gateway.
Be sure to read the firewall howto. There's also howto's on IPCHAINS
that are useful.
> 5. How difficult will it be to move the service when I move from my
> apartment into a house later this year?
Problematic. If your cable company offers the service at both locations,
it should be a snap. If it doesn't, you are hosed, and might need to get
DSL. If you change cable companies because of the move, all bets are
> 6. Are there kernel requirements? I currently run RH5.2 on my main box,
> but I'm getting another box that I can load anything on. I'll probably
> KRUD, but I still want to know what OS requirements might exist for
> cable modems.
I would update the kernel to get IPCHAINS. 2.2.14 should be sufficient,
and comes with the current RH release, and probably most other
distros (not that I keep track of such things). Be
> I'll save everyone the trouble of asking - I'll document my trials and
> tribulations and write something up for either my web site or another news
> site and let you know when its online.
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