DHCP Server Configuration

Unless you are a system administrator on a mid- to large-size network, you probably won’t ever have occasion to configure a computer to act as a DHCP server, and if you do, you probably have access to other documentation that is far more attuned to the peculiarities of your configuration than this book is. Windows provides a GUI-based utility called DHCP Manager for configuring the DHCP server.

Linux systems provide DHCP services through dhcpd, the DHCP daemon. Instructions for installing dhcpd vary according to the vendor. DHCP configuration information is stored in the configuration file /etc/dhcpd.conf.

The /etc/dhcpd.conf file contains the IP address configuration information that the DHCP daemon will assign to clients. /etc/dhcpd.conf also contains optional settings such as the broadcast address, domain name, DNS server address, and the addresses of routers. A sample /etc/dhcpd.conf file follows:

default-lease-time 600;
max-lease-time 7200;
option domain-name "macmillan.com";
option subnet-mask 255.255.255.0;
option broadcast-address 185.142.13.255;
subnet 185.142.13.0 netmask 255.255.255.0 {
range 185.142.13.10 185.142.13.50;
range 185.142.13.100 185.142.13.200;
}

As this chapter has already mentioned, DHCP service is often handled through a network device such as a router/firewall system. See the user manual for your home router for more on configuring DHCP. Router devices typically provide a web configuration interface (see Figure 12.4). Log in to your router’s configuration page to modify the DHCP configuration. In most cases, reconfiguration of DHCP isn’t necessary.

Figure 12.4. Configuring DHCP on a home router device.

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You might occasionally want to ensure that a device maintains a permanent address even though the rest of the network uses dynamic addressing. For instance, you might want to maintain a permanent address for a network printer so that the computers using it don’t have to keep relearning the address. Some routers provide a feature called IP Reservation that lets you associate a specific IP address with a specific physical (MAC) address. This feature ensures that the device will always receive the same IP address.