XGS-5240-Series User Manual

Configuration Guide of XGS-5240-Series
36-4
Chapter 36 DHCP Configuration
36.1 Introduction to DHCP
DHCP [RFC2131] is the acronym for Dynamic Host Configuration Protocol. It is a protocol
that assigns IP address dynamically from the address pool as well as other network
configuration parameters such as default gateway, DNS server, and default route and host
image file position within the network. DHCP is the enhanced version of BOOTP. It is a
mainstream technology that can not only provide boot information for diskless workstations,
but can also release the administrators from manual recording of IP allocation and reduce user
effort and cost on configuration. Another benefit of DHCP is it can partially ease the pressure
on IP demands, when the user of an IP leaves the network that IP can be assigned to another
user.
DHCP is a client-server protocol, the DHCP client requests the network address and
configuration parameters from the DHCP server; the server provides the network address and
configuration parameters for the clients; if DHCP server and clients are located in different
subnets, DHCP relay is required for DHCP packets to be transferred between the DHCP client
and DHCP server. The implementation of DHCP is shown below:
Fig 1-1 DHCP protocol interaction
Explanation:
1． DHCP client broadcasts DHCPDISCOVER packets in the local subnet.
2． On receiving the DHCPDISCOVER packet, DHCP server sends a DHCPOFFER packet
along with IP address and other network parameters to the DHCP client.
3． DHCP client broadcast DHCPREQUEST packet with the information for the DHCP server
it selected after selecting from the DHCPOFFER packets.
4． The DHCP server selected by the client sends a DHCPACK packet and the client gets an
IP address and other network configuration parameters.
DHCP CLIENT
DHCP SERVER
Discover
Offer
Request
Ack