[Tfug] Cox cable networking problem

[Shawn Nock]

Louis Taber wrote:
> Hi,
>
> I guess it is coming down to a network question.  The Motorola SurfBoard, as
> I now understand it is, well, not very clever.  
It is a cable modem, it does it's job (modulating and demodulating QAM) 
as well as any single purpose piece of gear. I however, believing the 
Internet is magic, find this to be very clever :P

> Perhaps the 64 computer
> limit is just an internal NIC list limit used for filtering packets coming
> in from the outside interface to be passed through the cable modem.  (I had
> initially made the assumption that it was a limit on its NAT or DHCP
> ability.)
>
>   
I heard that the user limit was to force the 'true believers' into 
putting a second on the house to finance a home data-centers w/ leased 
lines...

> Anyway my home network has:  Linux, Mac, and Windows computers.  A VoIP box
> and an HP print server.  (With occasional thoughts about Maxim TINIs,
> Lantronix X-ports, and Sun Ultras.)  I don't expect any trouble with getting
> DHCP addresses from COX 
>   
It sounds as though you want to use Cox's DHCP passed through the 
surfboard...
That would be possible but a really, really bad idea. Surfboard (unless 
you are talking about the new surfboard *Gateway* SBG1000; reference 
earlier comment on shady one-product uber-solution) are not firewalls 
and not routers and Win, Mac & Print Server + no protection from the 
Internet is a disaster!
> My inclination is to set up a non-routed network on the same physical LAN.
> Setting up my Linux system will be little problem.  How do-able is it under
> MS Window and Mac?  Is this a reasonable approach?  Any other suggestions?
>   

The Hard Way (pain, time, effort and pain) = Using Cox DHCP

    Your situation is complex enough to require 'basic' routing. Tips to 
get you started (warning! pseudo-explanation): Put on a pot of coffee... 
Set your Linux box up as a router (multiple NICs + enable packet 
forwarding + etc.) or buy the Linksys / Soekris and use them in a 
non-intended/tested role. You can use anything that is smart enough to 
do limited routing (If you are a patient man). Give your dumb clients 
the 'router' as the gateway. "Non-routed" is really 
"non-Internet-routed". (In this scenario your boxes hit the router and 
divert internal (e.g. 192.168.x.x) to the 'dumb' boxes and vice versa.
 
    That being said... Unless you *NEED* (not probable) to use Cox's 
DHCP for the vast majority of you home computers (expensive; they charge 
per IP on top of the base rate and, as discussed, possibly vulnerable) 
see below...

The Easy / 'Right' Way =
    There is no good reason not to do NAT + FW on the network you are 
describing. It is cheaper on a monthly basis, more secure, and the 
scenario is well tested/documented in the FOSS community, plus you have 
*total ultimate power* over the internal side of you network. Setup the 
Linux box you have (many howtos exist on this subject, most are 
reasonable well written) or buy a dedicated box (see previous post).

Shawn

P.S. If you are talking about the SBG1000 'Cable Gateway'  (I don't 
think cox offers it directly...), it would still be NAT + FW + MODEM... 
I imagine that unless 'one fell off the truck' the ~100USD Linksys 
Wireless router + 70USD SURFboard would be a better deal (Linksys has 
11g wireless, Moto has b-only).

P.P.S None of this post was intended to be a 'flame'... It sounds like 
you are on the cusp of wasting a bunch of time / trying out some cool 
routing techniques (I hope to save you that time with aid of humor!)

-- 
Shawn Nock (OpenPGP: 0xEF9B08E7)
Broadcast Engineer; KUAT Communications Group
University of Arizona
nock 'at ' arizona 'dot' edu