Huawei Quidway S5600 Series - Dhcp Relay Fundamentals; Introduction to Dhcp Relay; Usage of Dhcp Relay

Operation Manual - DHCP
Quidway S5600 Series Ethernet Switches-Release 1510 Chapter 3
DHCP Relay Configuration
Huawei Technologies Proprietary
3-1
Chapter 3 DHCP Relay Configuration
3.1 Introduction to DHCP Relay
3.1.1 Usage of DHCP Relay
Since the packets are broadcasted in the process of obtaining IP addresses, DHCP is
only applicable to the situation that DHCP clients and DHCP servers are in the same
network segment, that is, you need to deploy at least one DHCP server for each
network segment, which is far from economical.
DHCP Relay is designed to address this problem. It enables DHCP clients in a subnet
to communicate with the DHCP server in another subnet so that the DHCP clients can
obtain IP addresses. In this case, the DHCP clients in multiple networks can use the
same DHCP server, which can decrease your cost and provide a centralized
administration.
3.1.2 DHCP Relay Fundamentals
Figure 3-1 illustrates a typical DHCP relay application.
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
Switch ( DHCP relay
)
DHCP server
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
)
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
Switch ( DHCP relay
)
DHCP server
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
)
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
Switch ( DHCP relay
)
DHCP server
Ether net Inter net
DHCP
client
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
Switch ( DHCP relay
)
DHCP server
Ether net Inter net
DHCP
client
DHCP clientDHCP client
DHCP client
)
Figure 3-1 Typical DHCP relay application
DHCP relays can transparently transmit broadcast packets on DHCP clients or servers
to the DHCP servers or clients in other network segments.
In the process of dynamic IP address assignment through the DHCP relay, the DHCP
client and DHCP server interoperate with each other in a similar way as they do
without the DHCP relay. The following sections only describe the forwarding process
of the DHCP relay. For the interaction process of the packets, see
1.2.2 Obtaining IP
Addresses Dynamically
.
1) The DHCP client broadcasts the DHCP-DISCOVER packet.