Installing and Administering Internet Services

260 Chapter6

Dynamic Host Conﬁguration Protocol (DHCP)

Conﬁguration Overview

You should conﬁgure and administer the DHCP server using SAM. You

can also edit the conﬁguration ﬁles /etc/bootptab and /etc/dhcptab

manually, but it is not recommended. This section covers steps you must

take to conﬁgure DHCP using SAM.

Using SAM, you can conﬁgure DHCP to assign and distribute IP

addresses in three different ways:

• By Device or Pool groups (you deﬁne which devices are in these

groups)

• To individual devices

• Through a BOOTP Relay Agent

DHCP Device and Pool Group Conﬁguration

DHCP allows you to conﬁgure groups of similar client devices on a single

subnet. Each device in a speciﬁc group is automatically assigned an

available IP address from its group upon requesting booting information.

By creating various groups of devices you can compose each group with a

device type speciﬁc to that group. For example, you may want one group

to contain only printers. You may want another group to contain a

certain type of terminal.

The /etc/dhcptab ﬁle containsgroups of IP addresses that are managed

by DHCP, divided into two types: Pool Groups and Device Groups.

Pool Groups

A pool group is a collection of IP addresses on one subnet, available for

anonymous clients (most clients are anonymous). The pool groups are the

most common type of IP address groups. Here is an example pool group

entry in /etc/dhcptab ﬁle:

DHCP_POOL_GROUP:\

ba:\

pool-name=my_first_pool:\

subnet-mask=255.255.255.0:\

addr-pool-start-address= 15.13.100.20\

addr-pool-last-address= 15.13.100.29: