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Internet Access

girish rateshwar
Ranch Hand

Joined: Mar 04, 2001
Posts: 97
Dear all,
I have a NT Domain(srv-cats)i.e the primary domain controller. To this server i have a switch attached and this gives out connection to my linux server.
Onto the switch i also have an ADSL modem for the internet. How do i make my linux server access the internet.
Linux server is a part of my Domain.
I do not have much experience with configuration of internet. I have managed the printer, and Samba, but no success with Internet.

Tim Holloway
Saloon Keeper

Joined: Jun 25, 2001
Posts: 15950

like a lot of people, you mistake LAN services for HTTP. email and other Internet services. While they all run over the same network hardware, the protocols are quite different.
In order for a Linux machine to access the Internet, all it needs is to have a clear tcp/ip access path. I think that actually from the Internet's point of view, what you described was an ADSL modem hooked into a switched which then hooks into NT and Linux boxes.
That's most of what you need, but there's one thing more: routing. The Linux machine must have a valid TCP/IP address and an Internet gateway device to route Internet traffic through.
Some broadband modems have builting routers and/or firewalls. This is what you'd really want. In addition, the router must posess Network Address Translation (NAT) abilities. Either that or your ISP has to give you a second IP address for the Linux machine. Due to the way TCP/IP works, the router, NT box, and Linux box all have to have network addresses on the same subnet.
I guess what you need to find out is what sort of router configuration you're dealing with and if fixed TCP/IP addresses or DHCP address assignment is being used. Then you can work from there.

Customer surveys are for companies who didn't pay proper attention to begin with.
Hari Gangadharan
Ranch Hand

Joined: Mar 08, 2001
Posts: 73
Hi Girish -
Tim has explained it very well. But in more lay man terms let me add a little more.
1. The switch you are talking about is most probabily a router. If you have more than 1 computer sharing the internet then there is a very good chance that it is indeed a router.
2. First thing first - check whether your LAN card is setup correctly. You can check it in the Network settings. I am an old school guy and I would like to look at the /etc/sysconfig/network-scripts/ifcfg-eth0. Also you can verify this while booting the server - make sure that eth0 startup comes back OK. If you do not see "Starting eth0" then your card is not configured.
3. Once you have determined that the eth0 is working properly, check the IP address you are using for that. Did you make it DHCP or static. Normally a Linux server is assigned a static IP. You can first ping the IP address of another server in your domain. If ping comes back OK then your LAN setup is OK.
4. You might have not given the correct gateway address. Your server need to know how the packages are to be routed. Gateway address will be the IP address for your router. Once you set the gateway IP, you can do a test by pinging ( or ( If one of the ping has answer then you are connected to internet. If not, look under gateway address in the network settings.
5. Now try pinging or (name - not IP). If ping works, then you are ready to roll. You should now be able to access Internet. If ping fails, then you have not defined the DNS servers. Define it in the network settings. If you do not know the DNS server IP, contact your ISP or look at their web site.
[ June 27, 2003: Message edited by: Hari Gangadharan ]

<B>Hari Gangadharan</B><BR>Unix is user friendly..<BR>but it chooses to whom it is friendly with!
girish rateshwar
Ranch Hand

Joined: Mar 04, 2001
Posts: 97
I have checked the NIC. It pings to the domain controller.
Well all my windows clients make use of Microsoft Proxy Client which basically detects the proxy server.
I dont know wat exactly needs to be done for my linux server to be able to access the internet. :roll:
Well the adsl modem which is attached to the switch, is working fine with the windows client. When i try to access it via linux it gives me http 500 error.
Tim Holloway
Saloon Keeper

Joined: Jun 25, 2001
Posts: 15950

Pinging to the domain controller is meaningless in the sense of web page and FTP access, since they aren't domain services. However if you're attempting to connect to the Internet via the Microsoft proxy server, and the proxy server happens to the on the same box as your domain controller file server, then theat's meaningful in the sense that tcp/ip is, in fact working to the box. But it would still be working even if the file server was down, since it's the tcp/ip aspect that you're interested in, not the Windows file server program.
I'm still somewhat confused as to your actual setup here. If you expect to connect your Linux box to an NT box running proxy server, then the NT box goes via the switch to the modem/router, what you actually have to determine is:
1) Whether the NT box is in fact proxying for external hosts (other Windows and/or Linux boxes). It's possible that you could be only proxying for clients within the Windows box itself.
2) Whether that process is being blocked by firewall software either on the proxy server or on the Linux box. Depending on how you installed Linux, it may be working with a set of ipchains or iptables that forbids traffic over the proxy port. NT is infamous for being less protective, but you may have something blocking that side as well.
girish rateshwar
Ranch Hand

Joined: Mar 04, 2001
Posts: 97
Hi Tim,
Thanks indeed for your concern. Well to tell u wat the domain looks like.
1 Windows NT server, running the proxy server.
30 Windows NT + 20 Windows 2000 pro.
All the above clients connect to the proxy server via port 80.
The primary domain controller has a swtich to which it branches out connections to these clients via hubs.
Well coming back to the primary domain controller and the swtich is attached an adsl modem.
Now my question is: if the linux is running firewall, can it be a problem, cause i did a default installation for configuring firewall (medium).
question: is there any software that i need to install just like the windows clients have proxy clients installed on them.
Help appreciated
Tim Holloway
Saloon Keeper

Joined: Jun 25, 2001
Posts: 15950

Unfortunately, this is the kind of problem I could probably resolve in 15 minutes if I actually had hands on the hardware, but is gonna take forever to figure out by remote control.
All of the sudden what I'm seeing has changed from a home setup to an office environment. That changes some things, so I'll answer accordingly.
But first, I do have to reiterate that a Windows LAN domain (for example "TECSVCS") has nothing to do with Internet domains (""). It's very unfortunate that the same word is used, because the functions are nothing alike. Internet domains have no domain controllers. A LAN domain controller is involved in validating stations attempting to use LAN services, but an Internet client validates directly with the Internet servers it talks to (not the proxies, but the actual servers).
I actually haven't done much with Internet proxies, but all you should have to do to get Linux a machine working through a proxy is to point the browser to the proxy server. In Mozilla, this is done by issuing the Edit/Preferences menu command, opening up Advanced/Proxies under the Preferences dialog and aiming at your proxy server.
If you installed Red Hat, the "medium" security feature does allow access through port 80, as I recall. The exact rules for RedHat 8 or 9 should be in /etc/sysconfig/iptables .
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.
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