Very Computer

> I'm aware that many people have asked many variants of this problem, but
> I just can't seem to find the info I need to configure my linux box
> properly.

> I have three windows boxes(98,XP,XP) each with a configured network card
> and one linux box (Mandrake 8.1)with 3 network cards all configured and
> working properly.

>                               ----------------
> Win1 192.168.0.10 -----------|192.168.0.1
> Win2 192.168.1.10 -----------|192.168.1.1 linux box
> Win3 192.168.2.10 -----------|192.168.2.1
>                               ----------------
> All subnetmasks set to 255.255.255.0
> I can ping the linux box from any of the three windows machines, and I
> can shh into the linux box from any of the windows machines, and then
> from there ping all of the windows machines.

> What I want to do is to get the windows boxes to talk to each other. I
> am not sure if this is called IP forwarding, Network bridging, Routing,
> or none of the above, hence needing to ask for help.

> I have a very vague awareness of where the config files are in linux,
> and how to edit them, so I would really appreciate simple answers or
> references.
> Also what do I have to set the default gateway on the windows boxes to?

> Many many thanks

> Dominic

>>Hi,

>>I'm aware that many people have asked many variants of this problem, but
>>I just can't seem to find the info I need to configure my linux box
>>properly.

>>I have three windows boxes(98,XP,XP) each with a configured network card
>>and one linux box (Mandrake 8.1)with 3 network cards all configured and
>>working properly.

>>                              ----------------
>>Win1 192.168.0.10 -----------|192.168.0.1
>>Win2 192.168.1.10 -----------|192.168.1.1 linux box
>>Win3 192.168.2.10 -----------|192.168.2.1
>>                              ----------------
>>All subnetmasks set to 255.255.255.0
>>I can ping the linux box from any of the three windows machines, and I
>>can shh into the linux box from any of the windows machines, and then
>>from there ping all of the windows machines.

>>What I want to do is to get the windows boxes to talk to each other. I
>>am not sure if this is called IP forwarding, Network bridging, Routing,
>>or none of the above, hence needing to ask for help.

>>I have a very vague awareness of where the config files are in linux,
>>and how to edit them, so I would really appreciate simple answers or
>>references.
>>Also what do I have to set the default gateway on the windows boxes to?

>>Many many thanks

>>Dominic

> Is it your intention to have three separate subnets?  Or are you trying to
> set up a small single network?  If the former, then you have a routing
> problem and need to set up routes in your Linux box that directs packets
> to the appropriate subnet (card).  If the latter, then your easiest
> solution is to get a (cheap) hub, connect all four boxes to it and
> configure each to be in the same subnet.  Then no special routing is
> needed.

> Mitty

>> I want to do the former (three seperate subnets), basicly to help my
>> understanding networking. I think that I need to know four things
>> 1) Where are the routing tables in Mandrake
>> 2) What is the format for the routing tables
>> 3) What command restarts the network (I'm working remotly and don't
>> wan't to reboot the machine)
>> 4) What do I need to set on the windows boxes

> Not quite.

> (1) Since every subnet has its own interface on the linux box, this box
> already knows how to forward the traffic to the respective destinations.

> (2) That depends on who parses them.

> (3) Depends on Your distro.

> (4) Is the interesting part: On each win box, You need to point one
> (perhaps default) route to the corresponding IP of Your linux router.
> If this is not the default route, You could go with a netmask of /16,
> or add two routes with netmasks of /24.
> In this simple setup, You could even use host entries, which would be
> a netmask of /32.

> And, as others have said already, You probably need to enable ip for-
> warding on the linux router.

> Cheers, Jack.

> >> I want to do the former (three seperate subnets), basicly to help
> >> my understanding networking. I think that I need to know four
> >> things 1) Where are the routing tables in Mandrake 2) What is the
> >> format for the routing tables

>>Hi,

>>I'm aware that many people have asked many variants of this problem, but
>>I just can't seem to find the info I need to configure my linux box
>>properly.

>>I have three windows boxes(98,XP,XP) each with a configured network card
>>and one linux box (Mandrake 8.1)with 3 network cards all configured and
>>working properly.

>>                              ----------------
>>Win1 192.168.0.10 -----------|192.168.0.1
>>Win2 192.168.1.10 -----------|192.168.1.1 linux box
>>Win3 192.168.2.10 -----------|192.168.2.1
>>                              ----------------
>>All subnetmasks set to 255.255.255.0

> Why do you have three NICs in the Linux box? Given what you say you want
> to do, a much simpler configuration would be to put one NIC in each box
> and connect them together via a hub or switch. Give them all IP addresses
> on the same subnet (say, 192.168.0.0/24), and the Windows boxes can then
> talk to each other directly, without using the Linux box as a gateway.

>>What I want to do is to get the windows boxes to talk to each other. I
>>am not sure if this is called IP forwarding, Network bridging, Routing,
>>or none of the above, hence needing to ask for help.

> IP forwarding and routing are basically the same. Bridging is a bit
> different. Either will work in this case, but as I say, they aren't really
> needed if you simplify your configuration. If you really really want to do
> it with the physical connections you've got now, type this command in
> Linux:

> echo "1" > /proc/sys/net/ipv4/ip_forward

> You can add this command to a network startup script to make it persistent
> across reboots. (Most distributions store an option in a configuration
> file somewhere that'll enable it, but I don't recall offhand what it is
> for Mandrake 8.1.) You'll also need to tell each of your Windows boxes
> that the Linux box is the gateway system.

>>>I have three windows boxes(98,XP,XP) each with a configured network card
>>>and one linux box (Mandrake 8.1)with 3 network cards all configured and
>>>working properly.

>>>                              ----------------
>>>Win1 192.168.0.10 -----------|192.168.0.1
>>>Win2 192.168.1.10 -----------|192.168.1.1 linux box
>>>Win3 192.168.2.10 -----------|192.168.2.1
>>>                              ----------------

>> If you really really want to do
>> it with the physical connections you've got now, type this command in
>> Linux:

>> echo "1" > /proc/sys/net/ipv4/ip_forward

> IP forwarding is on, and the default gateway for the windows boxes is
> the linux box, but I still can't ping from one windows box to another.

>>>>I have three windows boxes(98,XP,XP) each with a configured network card
>>>>and one linux box (Mandrake 8.1)with 3 network cards all configured and
>>>>working properly.

>>>>                             ----------------
>>>>Win1 192.168.0.10 -----------|192.168.0.1
>>>>Win2 192.168.1.10 -----------|192.168.1.1 linux box
>>>>Win3 192.168.2.10 -----------|192.168.2.1
>>>>                             ----------------

>>>If you really really want to do
>>>it with the physical connections you've got now, type this command in
>>>Linux:

>>>echo "1" > /proc/sys/net/ipv4/ip_forward

>>IP forwarding is on, and the default gateway for the windows boxes is
>>the linux box, but I still can't ping from one windows box to another.

> I suspect that you're mistaken about one of those two things. In Linux,
> try typing the following command and report back the results:

> cat /proc/sys/net/ipv4/ip_forward

> If IP forwarding is enabled, the result will be "1"; if not, it'll be "0".
> It's also possible that you've got packet-filter firewall rules set up to
> block packets from being routed. Try typing this command to check:

> iptables -L

> You'll have to be root to use that one. You should see output like this:

> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination

> Chain FORWARD (policy ACCEPT)
> target     prot opt source               destination

> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination

> If any of the policies (especially FORWARD or OUTPUT) is not ACCEPT, then
> the system may be dropping forwarded packets. Likewise if there are a
> bunch of rules listed under these policies. If this is the case you'll
> need to track down your firewall script and modify it.

>>Is there anywhere on the linux system that logs are kept, so that I
>>might be able to see where the failure is when I try to ping through the
>>box.

> Linux doesn't normally log every packet it receives, although it can be
> configured to do so with the help of various tools (iptables, Snort,
> etc.). That said, most Linux log files are in /var/log or its
> subdirectories. Chances are they won't help you much in this case, but you
> can certainly check them. Try using the "tail" command to view the last
> few lines of a log file after performing an action that should produce
> logging.

>>Just to help my understanding, I want to explain what it is I think I am
>>doing, and then maybe somone could correct me.

>>Win1 (192.168.0.10)            ----------------
>>GateW(192.168.0.1)  -----------|192.168.0.1
>>                               |
>>Win2 (192.168.1.10)            |
>>GateW(192.168.1.1)  -----------|192.168.1.1  linux box
>>                               |
>>Win3 (192.168.2.10)            |
>>GateW(192.168.2.1)  -----------|192.168.2.1
>>                                ----------------
>>All Subnet masks 255.255.255.0

>>Say Win1 wants to talk to the linux box, it knows its on the same
>>network, so it just send IP packets with to (192.168.0.1)
>>If Win1 wants to talk to Win2, its not on the same network, so it looks
>>up the default gateway which is the linux box on (192.168.0.1), and then
>>sends out the IP packets with headers (192.168.1.10) to (192.168.0.1),
>>the linux box recieves these, and then knows that they are not for it,
>>but are to be forwarded to (192.169.1.10), so it sends them out from
>>(192.168.1.1) to Win2.

> That's the way it should work, yes.

>>What should the linux box think the default gateway is (Ie it is the
>>default gateway???)

> Given the information you've presented, it shouldn't have one. If it's got
> another network connection, though (say, to a DSL connection or even a PPP
> dialup link), the default gateway would be to it.

>>If I ping an internet address from Win1 eg google (216.239.33.101)
>>whilst I have a dial up connection established on Win1, how does that
>>box know  not to use the Gateway on the Lan (192.168.0.1) but use the
>>gateway at the end of the modem instead?

> You didn't say anything about dial-up connections. They're a potential
> monkey wrench, particularly on the Windows boxes. I don't know offhand
> what Windows does when you establish a dial-up connection. It might
> replace the default route, in which case it'd break your connection to
> other systems on your LAN, with the possible exception of the Linux box.
> In theory, another way to configure it is to make the dial-up
> connection's router the default route and to make your Linux box the
> route only for the 192.168.x.x addresses. I don't know offhand how you'd
> configure Windows to do this.

> If the Linux box has an Internet connection, this is much simpler -- but
> there is another complication. To let the Windows boxes have access to the
> Internet via the Linux gateway, you'd need to enable network address
> translation (NAT). You should be able to do this by typing the following
> command once the connection is up:

> iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

> This assumes that it's a PPP connection and that you've only got one PPP
> connection. You may also need to load a module by typing "modprobe
> iptable_nat" (without the quotes) before typing the above command. Also,
> I've never tried to do QUITE this thing, so there may be some factor I'm
> overlooking or forgetting.