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

A bootrequest from Client 1 is relayed from Server A to Server C through Server B. Server C
finds the client’s boot information in its database, and sends the bootreply back to server A.
Server A then sends the bootreply to the client.
NOTE: BOOTP clients can be booted over a gateway; however, the BOOTP server with the
relay information for the client must be on the same side of the gateway as the client.
File Transfer
The second BOOTP phase, which is the file transfer by the BOOTP client using TFTP, is optional.
Some BOOTP clients use BOOTP only for IP address resolution and do not use TFTP. If the boot
file is transferred, it must be publicly available.
DHCP Overview
DHCP (Dynamic Host Configuration Protocol) is an extension of the BOOTP protocol that defines
a protocol for passing configuration information to hosts on a TCP/IP network. The DHCP and
BOOTP daemons are a subsidiary of inetd, and are started or restarted automatically (that is, as
requests are passed to it).
The main advantage of DHCP is its capability to automatically allocate IP addresses to clients
booting on the TCP/IP network for the first time.
The DHCP server passes the IP information and other start-up information to clients, including
the name of the Domain Name Service (DNS) server. Additionally, DHCP passes the following
startup information:
• IP Subnet Mask
• IP Routes
• Broadcast IP Address
• DNS Server
• NIS Server
• NTP Server
Benefits of Using DHCP
Using DHCP reduces the labor involved in managing the network. Before DHCP, the network
administrator had to manually connect and configure every computer in a network.
Because the DHCP server automatically dispenses IP addresses and other configuration
information, the process of connecting a new computer to the network is much simpler. DHCP
is very flexible and allows the network administrator to set up the server one time to serve many
thousands of clients.
DHCP Components and Concepts
The primary components of DHCP are as follows:
• DHCP server
• DHCP client
• DHCP leases
DHCP Servers
The DHCP server dispenses and manages network IP addresses. It assigns IP addresses to clients
that are connecting to the network for the first time. When a client connects to the network, the
server automatically assigns it an IP address from an appropriate pool of IP addresses.
You can have multiple DHCP servers on your network provided their subnet pools do not
overlap. However, it is recommended that you have only one DHCP server for your entire
44 Overview