[linux-help] Re: Can't set up network

["Wayne M. White" <WWHITE1@xxxxxxxxxxx>]

At 10:46 PM 7/13/00 , you wrote:


> Jonathan Hall wrote:
>
> > Why do you have two NICs if you're only using one?
>
> You guessed it at the tail of your message - I want the linux box #1 to 
> become a
> firewall/server.  The eth1 card can be ignored for now - it has no cable 
> on it.  If
> I move the modem to eth1, I lose all internet access - well, I guess I 
> would still
> have it on box #1.
Allow me to have a go at this. I think what you want to do is connect eth0 
of the
Linux machine that you want to firewall/gateway through to the modem. Then
connect eth1 to the hub. By connecting the modem and all of the computers to
the hub you are allowing each machine to log in and get a IP via the hub. You
can then masquerade Linux #2 and Windows#1 through Linux#1.

On my net I give each machine a static IP for the network and the gateway 
machine
uses DHCP to acquire an IP from RR. You can load up your /etc/hosts file with
the IPs and names of the various machines and you're in business.


> Eth0 on box #1 and Eth0 on box#2 and the windows box are all hooked to the 
> hub.
> All three can access the internet (through the hub) so it seems logical 
> that they
> should be able to speak to each other.
>
> >
> > Naturally, the IP address of eth1 will not be pingable thru eth0 unless the
> > Linux box is set up as a gateway *AND* the other boxes know to use it as a
> > gateway.
> >
> > Imagine a city block with three houses, each with their own respective
> > addresses.... 100 Somestreet, 101 Somestreet and 102 Somestreet.
> >
> > One of the houses has a backdoor leading to the alleyway.... address 200
> > Otherstreet.
> >
> > Someone trying to find 200 Otherstreet when they're driving down Somestreet
> > will get lost.
> >
> > It sounds like your Linux box has two addresses... the one from RR
> > (24.x.x.x) and a private one on eth1 (192.x.x.x).  The reason the other
> > boxes cannot ping the 192.x.x.x address is b/c they're on the wrong
> > "street"... or, in real-world terms, they're on a different physical
> > network.
The two networks can't co-exist. You must separate them by getting the modem
off of the hub. Then you have two separate networks. Your local network
around the hub and the internet via the gateway machine.

> >
> > You either need to give eth0 the 192.x.x.x address, *OR* (usually
> > preferable), plug eth1 into the hub, and use the Linux box as a gateway to
> > the 'net (I assume this is what you're trying to accomplish in the longrun
> > anyway).
> >
> > Let me know if I've totally confused you by now... :-)
> >
>
> No, I think you cleared something up.  I set up eth0 on both linux boxes to
> 192.168.1.10 and 192.168.1.12 using netconf.  But when I boot up, they 
> both change
> to something like 24.92.x.x.  The 192.168 addresses disappear.
This is because they are logging onto RR vis the hub. DHCP will reset your 
IP to
the assigned one every time. Your firewall box has to be between your 
network and
the modem. Now, you could use the firewall box as a DHCP server and let it
assign IPs to each of the other machines on the network, however I have found
it much simpler, on a small network, to just use static IPs.


> 15 minutes later:  I switched the cables around.  Hoorah!  I can ping and 
> telnet
> from box 1 to box2 and box 2 to box 1.  Now I need to figure out windows 
> and how to
> get mail and internet through the linux box to windows.
>
> Thanks, Jon
With the above described setup each machine will be able to ping each of the
other machines on the network via the network. Each will be able to access the
internet via the firewall/gateway machine. What you're after is an IP 
Masquerade
setup. That how-to is very helpful, even to setting up the Windows machine.

I hope I haven't just confused things. What you're after is a very nice 
setup. I
run three to five machines on my local network and we can all access the 
internet
concurrently.

Good luck,

wayne



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