HP-UX IP Address and Client Management Administrator's Guide HP-UX 11i v2, HP-UX 11i v3

DHCP Configuration through BOOTP Relay Agent
In this method, DHCP distributes IP addresses to clients 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.
Figure 4-4 Relay Agent Scenario
Figure 4-4 illustrates a typical scenario of DHCP configuration though a BOOTP relay agent. In
Figure 4-4, when client2 broadcasts a boot request and the server containing the booting
information belongs to a remote network, the broadcast message is received by the local machine
known as the relay agent. The relay agent sends the message across the gateway to the remote
server, which in turns sends the boot information for client2 back to the relay agent. The relay
agent then broadcasts a message which is received by client2. The message contains the booting
information for client2.
A gateway can also be configured to serve as a relay agent, if the gateway DHCP-smart. However,
if the gateway does not have the knowledge of DHCP, then you must use a dedicated relay agent.
In Figure 4-4, client1 does not require a relay agent because client1 is on the same network as
the server.
NOTE: Most of the modern routers are DHCP-smart. The capability to relay is built into the
router, therefore you do not require a machine dedicated as a relay agent.
Configuring PING Timeouts
The DHCP server optionally sends a PING (ICMP echo) request to check if the IP address it
wants to assign to a client is in use. If the server does not receive the reply in a specified time,
the server assumes that the IP address is not in use. It then assigns that IP address to the client.
The specified time is the timeout value in milliseconds. The timeout value can be set using the
-p option.
The timeout value can be between 1 and 3000 milliseconds. By default, the timeout value is 3000
milliseconds.
You can use the following entry to specify the timeout value in the /etc/inetd.conf file:
# bootps
dgram udp wait root /usr/lbin/bootpd -p500
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