Dhcp Overview; Introduction To Dhcp - 3Com 5500-SI Configuration Manual

9

Introduction to DHCP

DHCP O
VERVIEW
With networks getting larger in size and more complicated in structure, lack of
available IP addresses becomes the common situation the network administrators
have to face, and network configuration becomes a tough task for the network
administrators. With the emerging of wireless networks and the using of laptops, the
position change of hosts also requires new technology. Dynamic host configuration
protocol (DHCP) is developed in this background.
Similar to BOOTP, DHCP adopts a client/server model, where DHCP clients send
requests to DHCP servers for configuration parameters such as IP addresses, subnet
masks, and default gateway IP addresses; and the DHCP servers returns the
corresponding configuration information. Both BOOTP and DHCP are encapsulated
with UDP. They adopt almost the same packet format.
BOOTP is suitable for relatively stable networks where hosts have fixed positions.
When using BOOTP, the administrators need to configure a BOOTP parameter file for
each host and will not change the file frequently. In comparison with BOOTP, DHCP
assigns IP addresses to hosts dynamically and quickly; that is, IP addresses are not
statically assigned.
A typical DHCP application includes one DHCP server and multiple clients (such as PCs
and laptops), as shown in Figure 32.
Figure 32 Typical DHCP application
DHCP client DHCP client DHCP client DHCP client
LAN LAN
DHCP client DHCP client DHCP client DHCP client
DHCP serv er DHCP serv er