New Here. IP Access List in Redhat Help.

bostonrake · 07-10-2007, 01:09 PM

Hello All,
I'm new to these forums as well as Linux. We have a Linux box at work that runs one of our main applications. Our network consists of 2 subnets. One of these subnets can access the linux box and the other cannot. The subnet that cannot access the box is x.x.240.x (I have x's for security reasons).

I know there is some sort of IP access list where you can input a range of IP's to allow access to the box. I know this because someone made this change once before to get our 240 subnet working, but when the linux box had some sort of update, this was wiped out. Any machine on this 240 subnet cannot ping the IP of the linux box.

Can anyone here point me into the right direction. Please know I do not know much about linux at all, so any help would be greatly appreciated.

Thanks,
Doug

b0uncer · 07-10-2007, 01:11 PM

Well, stuff like this can be configured with files like /etc/hosts.allow and /etc/hosts.deny or with iptables - see

Code:

man iptables
man hosts.allow
man hosts.deny

for further information.

bostonrake · 07-10-2007, 02:43 PM

can you tell me what man iptables does? I'm sorry, but I am so new to linux, I know pretty much nothing. I search the forums for iptables and found some information, but most of it was over my head. I basically just need to make sure the linux box will allow x.x.240.0 to x.x.240.254. That should do the trick for me.

Thanks,
Doug

bostonrake · 07-10-2007, 03:19 PM

Ok, I did some more research and found man iptables is the manual so to speak for ip tables.

I went to the terminal and typed man iptables and read some of the manual.

Back at the terminal I wanted to list the iptables so I typed iptables -l and it says it is not a valid command.

Now, I know there is some login called "root" I don't think the box is logged in as root and maybe this is why I can't list the ip tables?

I don't want to bring this server down or restart it because it is necessary to be up 24/7. How can I run iptables -l as root?

If I'm not thinking right here, please let me know... again, I'm new to all of this.

Thanks!
Doug

bostonrake · 07-10-2007, 03:34 PM

Ok, learned a little bit more. I found after I opened terminal I needed to become root by typing su -

I became root and then did iptables -L and it listed the tables or I should lack there of. It doesn't look like there is a table.

So, now I'm back to square one. I need to figure out why the 240 subnet can't ping and reach the linux box.

Thanks,
Doug

Matir · 07-10-2007, 03:50 PM

My guess is that there exists a routing issue. Which subnet is the box present on? If it's not on the .240.x subnet, you'll likely need to adjust your routers configurations. Can the two subnets talk to each other on other computers?

bostonrake · 07-10-2007, 04:13 PM

Yea, other computers can talk to each other on the 2 different subnets. It is just the 240 subnet is not able to talk to the linux box. Now the linux box I believe can ping 240, but 240 cannot ping the linux box.

At first I thought it was a routing issue too, however we had a third party contract company come in to work on something else and while they were here we told them about the issue. They got the 240 subnet to communicate with the linux box by doing something on the linux box. Unfortunately when we had a TopForm (the application we run on linux) update, it must of wiped whatever change this contracting company did. The reason I say that is because the 240 subnet stopped being able to communicate with the linux box after the update.

There doesn't appear to be any iptables setup. I imagine this is the default? Maybe it is just a simple iptable setup, but I don't want to screw anything up. The whole company relies on being able to hit the TopForm app on the linux box.

Doug