Using a graphical user interface

1. From the Control Panel, open the Network Connections applet.
2. Double-click the connection you want to configure.
3. Click the Properties button.
4. Double-click Internet Protocol (TCP/IP).
5. To enable DHCP, select Obtain an IP address automatically. To use a static address, select Use the following IP address. Then configure the IP address, subnet mask, and default gateway.
6. Click OK until all windows are closed.

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You have some servers or other machines to which you want to assign static IP addresses. You can use /etc/hosts, but it’s a bit of bother to edit /etc/hosts on each of the zillion PCs you’re responsible for. Can you do it in dhcpd.conf?

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In Windows, open Control Panel -> Networking, then open the Properties box for TCP/IP. Check “Obtain an IP address automatically.”

It’s just as easy in Linux; the only hard part is that every distribution puts the configuration file in a different place. In Red Hat and Fedora, edit /etc/sysconfig/network-scripts/ifcfg-eth0 as follows:

TYPE=EthernetDEVICE=eth0

BOOTPROTO=dhcp

ONBOOT=yes

DHCP_HOSTNAME=stinkpad

On Debian, edit /etc/network/interfaces as follows:

auto loiface lo inet loopback

auto eth0

iface eth0 inet dhcp

You may wish to use a graphical configuration tool. On Red Hat and Fedora, use system-config-network. KDE and Gnome have their own GUI configuration tools (as does practically every Linux distribution), so you won’t be short of choices. Another option is netGo, a system-independent network configuration utility that lets you create profiles for easily connecting to different networks

Install and configure dhcp. You can get the source tarball from http://www.isc.org. RPMs and Debian packages are also available; just look for packages named "dhcp." Configure client PCs to point to your dhcp server, and you’re done.

A dhcp server can feed all network configuration data to the clients. The configuration file is /etc/dhcpd.conf. Here is a sample configuration:

# /etc/dhcpd.conf

default-lease-time 259200;

max-lease-time 518400;

subnet 192.168.1.0 netmask 255.255.255.0 {

   option subnet-mask 255.255.255.0;

   option broadcast-address 192.168.1.255;

   option routers 192.168.1.1;

   option domain-name "test.net";

   range 192.168.1.50 192.168.1.100;

   option domain-name-servers 152.163.199.56, 198.83.210.28;

}

This is pretty straightforward. The lease times are in seconds, so the minimum and maximum in this example are three days and six days. "Option routers" points to your Internet gateway, or the gateway to the subnet. A pool of 50 addresses is made available in the "range." The name servers are either your own private caching server or servers, or the name servers at your ISP.

This example uses private, nonroutable IPv4 (Internet Protocol Version 4) addresses. Here are the private IPv4 address classes, in both dotted-quad and Classless Inter-Domain Routing (CIDR) notation:

10.0.0.0     - 10.255.255.255  (10/8)

172.16.0.0   - 172.31.255.255  (172.16/12)

192.168.0.0  - 192.168.255.255 (192.168/16)

These are for use on private networks, so you’ll select your subnet ranges from these.