computers, crossover cables & internet, Oh My!
 

If this question has been posted in an another place I apologize, I have looked through the posts and not found what I'm looking for or may of over looked it. If it has been just please post the link and I'll work off of that post. Mean while back to the question. Here is what I'm trying to accomplish and what I have so far.

since I can't put a graphic here to show what I've got I'll try and explain it. 3 computers - 2 with two nics and 1 with one nic and 1 computer with connection to the INTERNET

A has 2 nics
<a1> --> 172.x.y.5
<a2> --> 172.x.y.6
L has one nic
<l1> --> 172.x.y.10
T has 2 nics
<t1> --> 172.x.y.15
<t2> --> 66.xx.yy.zz

<a1> connects to <l1> via X/over cable
<a2> connects to <t1> via X/over cable
<t2> connects to the WWW

What I'm trying to accomplish is to be able to have all 3 system share NFS connections to each other but only have T have incoming access only from several Win2k systems on the 66.x.y.z network. The 2k systems will be logging in and authentication with from T Samba and the information that each user would pull would come from the other 2 systems. The reason for the x/over cables is due to the fact the dept. refused to spend 'any; money on parts for this so I'm having to build this with what is there and no hubs or switches are available.

I'm not sure how to set it up to lock out all incoming traffic to where the only thing anyone will have access to from their 2k boxes is the system they authenticate off(which will be set up to verify the user is supposed to be on that network of computers) of and their specific 'home' folder that would be located on any 1 of the 3 systems. The 2k systems at the present time all have static IP addresses

I know this is pretty convoluted and there is probably a better way of doing this but this is what I've got, any constructive criticism would be greatly appreciated. And, if anyone needs any further information about this please post and let me know, hopefully this will be clear.

Does that setup actually work? It seems to me you're going to have all kinds of problems reaching boxes that you're not directly connected to because you have multiple interfaces on the same subnet plugged directly into different boxes and interfaces (also on the same subnet). You would do well to put each crossover cable connection on it's own subnet (you should need a /30, because IIRC you need one IP for the network number and one IP for broadcast).

So an example would be that two interfaces share 172.16.0.0/30. The first interface has 172.16.0.1, and the second has 172.16.0.2. You shouldn't (again, IIRC) use 172.16.0.0 (because it's the network number) and also don't use 172.16.0.3 (it's the broadcast address). The next crossover connection would be 172.16.0.4/30 and the two IPs would be 172.16.0.[5,6].

Machine A will need to have IP forwarding enabled so that T can pass traffic to L and vis versa. You will probably need a static route on T that points 172.16.0.0/29 to interface t1. The default route for L should point to the IP of a1 and the default route on A should point to the IP of t1. You'll need a firewall enabled on T to prevent traffic from being able to flow all the way through.

As for how to setup the mounts... well, good luck there. Someone with more Samba experience than I will have to help you out.

By the way, a minor nitpick I know, but "WWW" stands for "World Wide Web (of HTML sites)", so what you really mean is t2 connects to the "Internet" (the global Interconnected Network). The WWW is just a sub-set of the Internet, and it refers to websites only.

sorry for the slow response 12 hr days being a phone drone take a bit out of a person. Anyway, if I am reading your reply correctly what I did should be correct. My networking skills in this matter are pretty much a bit lacking to say the least, but here is what I 've got.

A has 2 nics
<a1> --> 192.168.x.5
<a2> --> 172.x.y.5
L has one nic
<l1> --> 192.168.x.10
T has 2 nics
<t1> --> 172.x.y.10
<t2> --> 66.xx.yy.zz

<a1> connects to <l1> via X/over cable
<a2> connects to <t1> via X/over cable
<t2> connects to the Internet

This maybe a really fundamental networking question but when you referenced 172.16.0.0/30 that is saying that I can you 176.16.0.1 through 176.16.0.30 correct? Obviously 0 and 31 not usable. And, would that be the same as having a subnet mask of 255.255.255.224?

172.16.0.0/30 (30 network bits, 2 host bits) would be written 255.255.255.252.

usefull ??

Network calculator
http://www.telusplanet.net/public/sparkman/netcalc.htm

Very useful for figuring out subnet masks and IP ranges. thank you!

Well it seems that I've got one system on and able to access the intranet. I am still not able to see the other systems that I have connected to each other. The system with the 66.x.y.z address is able to access the intranet (this is just fine for now). I changed the system that were connected via crossover cables to a different net (see previous post). What is the really silly stupid thing I'm missing here?

When I say "not able to see" I mean that I'm not able to ping any of them by either IP or name. All of the systems have identical /etc/hosts and the /etc/host.allow have been set to ALL:ALL (for now) and /etc/hosts.deny are currently blank.