Installing and Administering Internet Services

Chapter 6 261
Dynamic Host Configuration Protocol (DHCP)
Configuration Overview
In the example above, ba indicates the broadcast flag has been turned on.
Most clients need this flag, so it will be in most pool group entries. The
pool-name is a label that helps the system administrator identify the
pool group. The client is not aware of this name. The beginning and end
of the address range in the pool is defined by addr-pool-start-address
and addr-pool-last-address. The pool group in this example contains
10 addresses on the 15.13.100 subnet: 15.13.100.20 through
15.13.100.29.
There can only be one pool group per subnet. The pool group is the
default IP address group.
Figure 6-3 Devices Can be Configured as Part of a DHCP Group
In Figure 6-3, assume that a particular group has been configured so
that Client1, Client2, and Client3 all belong to this group. This means
that each device in this group will have the same group name and will be
given an IP address that is within the group’s IP address range. The IP
addresses within the group’s range make up what is known as a pool of
addresses. When Client1, Client2, or Client3 perform a boot request,
they will automatically be assigned an IP address not already in use
from this pool.
DHCP allows you to exclude certain addresses within a group if you do
not want them used.
You can also define many values for the devices of a group including
address lease times, DNS servers, NIS servers, and many other optional
parameters. See the example “Complex DHCP Pool and Device Group
Files” on page 262.
DHCP Device Group
You can create a device group by configuring similar client devices and
specifying a unique IP address range for the group of client devices. The
device group differs from the pool group in that all the clients in the
group must be the same. For example they must all be printers or X
DHCP
Client1
Client2
Client3
Server
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