Installing and Administering Internet Services

264 Chapter6
Dynamic Host Configuration Protocol (DHCP)
Configuration Overview
Figure 6-4 DHCP Devices Can Have Fixed IP Addresses
In Figure 6-4, assume that you have configured a DHCP group (group A)
to include Client1 and Client2, meaning that each will receive an IP
address from a pool of available addresses at boot request. However, you
configured Client3 and Client4 to have fixed IP addresses. Client3 and
Client4, therefore, will be assigned the addresses you configured for
them upon boot request. Client3 and Client4 will always be assigned
these same addresses unless you change the configuration.
DHCP also allows you to define many optional parameter values for
clients with fixed addresses. Fixed address devices are configured in
/etc/bootptab file. Again, it is best to use SAM to configure the
/etc/bootptab file.
For specific details on configuring DHCP to distribute IP addresses to
individual devices, see “Configuring a DHCP Server to Distribute IP
Addresses to Individual Devices” on page 270 .
DHCP Configuration through BOOTP Relay Agent
The third method DHCP distributes IP addresses to clients is through a
BOOTP Relay Agent. A BOOTP Relay Agent is a machine on the local
network that forwards boot requests from a DHCP or BOOTP client to a
configured DHCP or BOOTP server.
DHCP
Client1
Client2
Client3
Server
DHCP
DHCP
DHCP
Client4
DHCP
Group A
Group A
Fixed
Fixed
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