David Nordlund wrote:
>
> Hi, I've got a system arrangement that goes something like this.
> I have computer A(Mandrake 7) and computer B(Corel 1) connected to a hub.
> Also connected to the hub is a cable modem, C. C is good friends with
> A, but isn't really on speaking terms with B.
> (The cable modem is set up for the MAC address in computer A)
You should try resetting the cable modem (if it is a Motorola, there's a
reset tab on the back) while it is connected to the hub. It should
reacquaint itself with its new friend, the hub.
Having said that, this is not a MAC address issue. I'm not surprised
you're having problems, you've made some bad assumptions (and I suspect
you're also making your cable ISP's network not very happy =) ).
But I'm interrupting.
> Each computer has one ethernet card. I can get A talking to B if
> I ifconfig eth0 to a private network IP (192.168.0.1) but then it won't
> talk to the cable. B won't talk to A if A is set to the IP address that
> the cable modem gives it(via DHCP).
*argh*
This is bad (you are sending garbage private IP packets out onto the
loop), and it won't work.
Let's start from the beginning.
Your cable ISP gives you *one* DHCP assigned IP address, and it passes
you this IP address through the cable device. The network hardware on
their end can be configured to pass multiple DHCP addresses to *one*
cable device, but you're not paying for this and you didn't get it. What
does this mean? You can only have *one* interface connected to the cable
modem. Based on the scenario you described above, you have two.
Survey says?
*BZZZZZZZZT*
Item two: Let us assume that it's even *possible* for you to assign a
separate IP to B. Now you have put two machines which are on *different*
IP networks (one on 192.168.0.0 and one on 24.0.0.0) on the same
*physical* network. They will most definitely be ignoring each other,
you can count on that.
Survey says?
*BZZZZZZZZZT*
Enough Family Feud references -- let's fix this.
> Is it possible to get A & B talking to each other while A is on
> the net? If so, I assume I can masquarade B through A.
Make sure you're clear about what masquerading is. In order to
masquerade, you need a gateway machine (essentially a router) between
your private network (192.168.0.0) and the public Internet (here in the
form of network 24.0.0.0). This means that your hub *cannot* be on the
public side! Only *gateway* devices can have a presence on the public
network.
In masquerading, the gateway machine will rewrite all the packet headers
destined for the public network so that they have a valid, public IP
address on them (this is, in your case, the IP that is assigned to you
via DHCP), and will rewrite the returning packet headers with the
appropriate private IP address before sending them out onto the local
network.
A possible scenario is this:
Machine A has *two* (sorry) ethernet adapters, one *external* (we'll
call this eth0, which you connect to the cable modem) and one *internal*
(called eth1, which is connected to B using a crossover cable or
connected to the hub, in which case you can add as many other machines
as the hub will handle).
Try to think in terms of interfaces. It is the interface that has the IP
address.
So here, eth0 has the IP address (on network 24.0.0.0) assigned to it
via DHCP, and eth1 has a static address on the private network
192.168.0.0. It's usually wise to use 192.168.0.1, it cuts down on
confusion. This is becomes the default gateway for the machines on your
private network. The gateway machine will then forward packets as
appropriate between the private and public networks, providing you have
IP forwarding enable and ipchains configured properly.
The machines on your network (based on our example) can have any address
from 192.168.0.1 to 192.168.0.254. The terminating octets of 0 and 255
are reserved as network numbers and broadcast addresses respectively.
So, to make a long answer short, yes, you will need an additional
network card -- but if you are going to set up IP masquerading, you have
some reading to do =).
Start with the IPCHAINS how-to. You can find it at www.linuxdoc.org.
-Stephen-
