So I wanted to be able to configure “static” IP addresses for all the computers in our network, plus give out IP addresses within a range for guest machines. I needed DHCP (Dynamic Host Configuration Protocol) for that.

I also wanted to be able to boot a machine off the network and install Linux on it without having to connect an optical drive. That’s what PXE (Preboot Execution Environment) is for. Together with Kickstart, I can automatically setup a Linux web server, workstation, etc. without even touching the keyboard (not really).

TFTP (Trivial File Transfer Protocol) and HTTP are simply the protocols used together with PXE to transfer some files to get a machine to boot off the network.

Anyway, let’s get started.

So first thing is to install dhcp:

yum install dhcp

The configuration files for DHCP go in the /etc/dhcp/ directory. Since I only need ipv4, I’ll only be configuring dhcpd.conf and not dhcpd6.conf. Anyway, there’s a bunch of templates in /usr/share/doc/dhcp-x.x.x/ if you want. My configuration is below:

authoritative;

subnet 10.0.0.0 netmask 255.255.255.0 {
    range dynamic-bootp     10.0.0.240 10.0.0.250;

    option domain-name      "i4asiacorp.lan";
    option domain-name-servers  10.0.0.2, 10.0.0.3;

    option routers          10.0.0.1;

    default-lease-time      7200;
    max-lease-time          14400;
}

You always need the “authoritative;” option.

So I setup a “subnet” section, but I believe if you only have one network, you can put all these options in the “root” of the configuration file.

The “range” option is whatever IP addresses you want to provide to your network. The “dynamic-bootp” option in the range simply says that this range is also to be used for booting up network devices that support the protocol. Most machines these days do.

“option domain-name” is simply the local domain. My company only has a local private network, so I like to use .lan for that. I don’t really want to mix it up with our website at i4asiacorp.com.

“option domain-name-servers” is the DNS servers you will be using. Our network has two separate servers for this. If you just want to provide Internet access, perhaps setting it up to use something like Google’s DNS (8.8.8.8, 8.8.4.4) or OpenDNS (208.67.222.222, 208.67.220.220) will do.

“option ruters” is whatever is your gateway to the Internet.

“default-lease-time” is how long to provide the lease if the client doesn’t specify an expiration and “max-lease-time” is the maximum lease time ever. So for me, that’s 2 and 4 hours respectively. I could probably optimize that.

After you set the proper IP addresses for your network, restart dhcpd and set it to start on server boot up:

service dhcpd restart && chkconfig dhcpd on

So I mentioned I like setting up “static” IP addresses for the computers on our network. Why? Well, I like to make sure I know what machine is accessing what. But I also don’t want to manually configure everything. So I use DHCP for this.

So how do you do this? Well, first thing you need is the MAC Address of the network device. You can get this in Linux or Mac by running the command:

ifconfig

and in Windows by:

ipconfig /all

It should look something like aa:bb:cc:dd:ee:ff. So now that you have it, you need to know what IP address you will be providing it. Then you’ll simply add that configuration to the end of dhcpd.conf. So, if you want to provide the machine with MAC Address aa:bb:cc:dd:ee:ff with IP address 10.0.0.123, you add the following configuration:

host 123 {
    hardware ethernet aa:bb:cc:dd:ee:ff; fixed-address 10.0.0.123; }

For the “host 123” the “123” part is simply whatever you want to call the section. For our internal setup, I use the name of the user. So if we had a user Michael, then I set the option up as “host michael”.

Then remember to restart dhcpd: service dhcpd restart

Umm, I think I’ll do the PXE stuff in another post to keep things short. Sorry about that. I have a tendency to ramble.