H3C Technologies H3C S3100 Series Switches - Manual (Page 363)

Operation Manual – DLDP
H3C S3100-52P Ethernet Switch Chapter 3 DHCP/BOOTP Client Configuration
3-2
DHCP Client
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Server
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP Client
DHCP Server
DHCP Client
DHCP Client
DHCP Client
DHCP Server
DHCP Server
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
DHCP_D
iscover
DHCP_R
equest
DHC
P_Of
fer
DHC
P_AC
K
DHCP_R
enew
DHC
P_AC
K
Figure 3-2
The interaction between a DHCP client and a DHCP server
To obtain a valid IP address dynamically, a DHCP client exchanges different
information with the DHCP server in different phases. Usually, the following three
phases are involved.
1) The DHCP client accesses the network for the first time
When a DHCP client accesses a network for the first time, it goes through the following
four phases to establish connections with the DHCP server.
z
Discovery. The DHCP client tries to discover a DHCP server by broadcasting
DHCP-DISCOVER packets in the network. Only DHCP servers respond to this
type of packets.
z
Offering IP addresses. Upon receiving DHCP-DISCOVER packets, each DHCP
server selects a free IP address from an address pool and sends a DHCP-OFFER
packet that carries the selected IP address and other configuration information to
the DHCP client.
z
Selecting the IP address to be used. The DHCP client only accepts and processes
the first-arrived DHCP-OFFER packet (if multiple DHCP servers send
DHCP-OFFER packets to it), and broadcasts a DHCP-REQUEST packet to each