Static ip

Supporter1984 · 01-09-2008, 02:11 PM

Hi,
I have my home network configured with DHCP (linux web server, 2 windows hosts) and now i want to have static ip adresses. My DHCP server is the router, not the linux server. How can i do that.

Thanks

Emerson · 01-09-2008, 02:20 PM

Quote:

Originally Posted by Supporter1984

Hi,
I have my home network configured with DHCP (linux web server, 2 windows hosts) and now i want to have static ip adresses. My DHCP server is the router, not the linux server. How can i do that.

Thanks

Based on information you supplied I'd say you have to edit some configuration file in your Linux box. If you tell us what distro you are using then we can tell you what file it is. If you have a GUI installed then there may be a GUI tool for this.

tronayne · 01-09-2008, 02:32 PM

On the Linux side of the world, you need to edit the file that contains the settings; it will be named something like inet1.conf or similar and will be in the directory containing your system's start up files in /etc. If you grep for the file name, there should be a pattern like DHCP_HOSTNAME in the file (you will need to disable that, by the way).

Here's an example of inet1.conf set up for fixed IP:

Code:

# This file contains the configuration settings for network interfaces.
# If USE_DHCP[interface] is set to "yes", this overrides any other settings.
# If you don't have an interface, leave the settings null ("").

# You can configure network interfaces other than eth0,eth1... by setting
# IFNAME[interface] to the interface's name. If IFNAME[interface] is unset
# or empty, it is assumed you're configuring eth<interface>.

# Several other parameters are available, the end of this file contains a
# comprehensive set of examples.

# =============================================================================

# Config information for eth0:
IPADDR[0]="192.168.1.20"
NETMASK[0]="255.255.255.0"
USE_DHCP[0]=""
DHCP_HOSTNAME[0]=""

# Config information for eth1:
IPADDR[1]=""
NETMASK[1]=""
USE_DHCP[1]=""
DHCP_HOSTNAME[1]=""

# Config information for eth2:
IPADDR[2]=""
NETMASK[2]=""
USE_DHCP[2]=""
DHCP_HOSTNAME[2]=""

# Config information for eth3:
IPADDR[3]=""
NETMASK[3]=""
USE_DHCP[3]=""
DHCP_HOSTNAME[3]=""
            
# Default gateway IP address:
GATEWAY="192.168.1.1"
<more stuff below this, nothing to do with fixed IP>

That is, the fixed IP address of the system is 192.168.1.20, the gateway address (the router) is 192.168.1.1 and the netmask is 255.255.255.0. You system will probably have values in the DHCP fields for eth0. Don't just copy the above, look for your file and read through any notes that may be in it. You may want to add your system name and the fixed IP address you've chosen (you may not want 192.168.1.20) in /etc/hosts.

On the Windows side of the world... well, can't really help your there but I run my Linux boxes fixed IP and a Windows (XP) machine as DHCP to the same router and it all works fine. Other than that, can't help you with Windows.

Hope this helps some.

Emerson · 01-09-2008, 02:38 PM

Cool, tronayne.

Here's the same for Gentoo:

Code:

 ~ $ cat /etc/conf.d/net

config_eth0=( "192.168.2.2 netmask 255.255.255.0 brd 192.168.2.255" )
routes_eth0=( "default gw 192.168.2.254" )

Supporter1984 · 01-09-2008, 06:52 PM

Thanks for the help so far. My distro is Slackware 12.

I have to change my router setting, am i right? I have to disable DHCP?

Emerson · 01-09-2008, 07:02 PM

No you don't. You may want to reserve some IP range for static addresses.

Supporter1984 · 01-09-2008, 07:06 PM

So you are saying that i dont need to disable the DHCP server. Do i have to have my static ip's on the DHCP ip range?

Thanks for the help.

Emerson · 01-09-2008, 07:13 PM

You have to have your static IP address on the same subnet. For instance, if you have net 192.168.1.0/24, (mask 255.255.255.0) then use static address 192.168.1.something.

KnightHawk · 01-09-2008, 07:21 PM

Quote:

Originally Posted by Supporter1984

So you are saying that i dont need to disable the DHCP server. Do i have to have my static ip's on the DHCP ip range?

Thanks for the help.

No, in fact you should remove them from the range. Or hard-code they're assignments with mac address.

Supporter1984 · 01-09-2008, 07:21 PM

Quote:

Originally Posted by Emerson

For instance, if you have net 192.168.1.0/24,

What do you mean with that?

Emerson · 01-09-2008, 07:30 PM

Quote:

Originally Posted by Supporter1984

What do you mean with that?

That's a very good question.

I recommend some reading: http://www.ipprimer.com/overview.cfm

arubin · 01-10-2008, 03:22 AM

I have done this recently on Slackware.

You need to run netconfig as root and answer the questions.

On the router side you should be able to set it to limit the addresses it offers with dhcp. You then set your static IP outside this range.

arubin · 01-10-2008, 03:32 AM

A few more thoughts.

The way you do this depends on whether you want your router to offer dhcp to other machines or not. So you could set up static IP on your linux box and, when you are sure this is working turn dhcp off on the router.

An alternative approach is to the one I suggest in my earlier post. Restrict the range of addresses the router offers, up to for example 192.168.1.200 and set your static address for 192.168.1.201. The reason for restricting the range is to make sure that 192.168.1.201 is not given to another computer while yours is off.

Alternatively you set your router to always associate your PC with a particular address. You still connect to it dynamically with dhcp but the router always allocates the same address. This way you need to configure the router but do not need to change anything on the PC.

tronayne · 01-10-2008, 08:19 AM

The inet1.conf example I gave you above is from Slackware 12. If you have, say, a Linksys router, it by default starts DHCP addresses at 192.168.1.100; 192.168.1.2 through 192.168.1.99 can be used for fixed IP addresses (192.168.1.1 is the gateway address, don't fiddle with that). As suggested above, you can log in as root and use the netconfig to set this rather than manually editing inet1.conf

If you set your server to 192.168.1.10 you should be fine and your Windows machines will use 192.168.1.100, 192.168.1.101, etc. Don't forget that you'll need to reboot after making the changes (rebooting is the easiest way to have the setting take effect).

This assumes that you did not set your router to any other addresses or that it defaults to 192.168.1.X -- you may need to check that by pinging the address 192.168.1.0 for a response (and if you don't get one, use a browser to look at the router's settings referring to the manual that came with it).

It really is this easy, just edit inet1.conf (or run netconfig) and reboot.

arubin · 01-10-2008, 08:36 AM

When I did this my main problems were with setting the gateway address and with setting the DNS address that the netconfig script offers. I think that in the end I found that it worked if I entered the same address as gateway for DNS. Until I got that right I could connect to the router but not to the Internet.