[NCLUG] Question on Cable modems

[Benson Chow]

When I was renting a room from a friend's house, we had one cablemodem 
from Comcast(Fort Collins) and both of us grabbed unique IP addresses from 
the cablemodem without a router, with a plain old hub hooked up to the 
cablemodem.  However it did cost us an extra $5/mo for this feature so 
that both of us would have public IP addresses.  I wanted to run a server 
and he didn't want to be blocked from doing the same so that was our best 
solution.

I don't know about what they do now though.  This was around 5 or 6 years 
ago.

In any case, both machines need unique IP addresses regardless if they're 
'public' or 'private' addresses.   For 'public' addresses, Comcast will 
happliy lease you additional addresses, at least in the past they did.  To 
have 'private' addresses or if Comcast no longer rents additional IP 
addresses, you'll need to have a NAT router.  I currently have both sets 
of public and private addresses (under Qwest DSL, but the concept is the 
same) and my private NAT addresses/routing are served by a Linksys WRT54G 
router.

Which way to go depends on your needs as well as Comcast's services, do 
you need two independent public IP addresses so both can be accessed 
independently with well-known port numbers (or if your VPN software has 
draconic security measures), or will NAT/PAT be sufficient and save you a 
few bucks per month?

You'll definately need additional hardware and/or software for the NAT/PAT 
solution past the hub, a hardware solution is recommended so you can 
reboot either computer without affecting the other's network connection.

As for more "working solutions" I setup a 24/7 P166MMX Linux machine as a 
router for my sister in MD since it was lying around.  This machine is 
more than enough for Comcast cablemodem, I don't really notice a slowdown 
through it's NAT/PAT tables.  Mainly the machine's big enough so that my 
sister can also run Bittorrent off of it (I scrounged up 40MB of RAM for 
it before, it running well except for some swapping with Python+BT, so I 
found more and upped it to 64M just for that :-)

-bc