Configuration Guide Configuring DHCPConfiguring DHCP
Figure 4-7
A host requests an IP address through DHCP as follows:
9. A host broadcasts a DHCP discover packet to find DHCP servers in a network.
10. DHCP servers unicast/broadcast (based on the property of the host packet) DHCP offer packets to the host,
containing an IP address, a MAC address, a domain name and a lease.
11. The host broadcasts a DHCP request packet to formally request an IP address.
12. A DHCP server sends a DHCP ACK unitcast packet to the host to acknowledge the request.
A DHCP client may receive DHCPOFFER packets from multiple DHCP servers, but usually it accepts only the first
DHCPOFFER packet. Besides, the address specified in a DHCPOFFER packet is not necessarily assigned. Instead,
it is retained by the DHCP server until a client sends a formal request.
To formally request an IP address, a client broadcasts a DHCPREQUEST packet so that all DHCP servers sending
DHCPOFFER packets may receive the packet and release OFFER IP addresses.
If a DHCPOFFER packet contains invalid configuration parameters, a client will send a DHCPDECLINE packet to the
server to decline the configuration.
During the negotiation, if a client does not respond to the DHCPOFFER packets in time, servers will send DHCPNAK
packets to the client and the client will reinitiate the process.
During network construction, Ruijie DHCP servers have the following features:
Low cost. Usually the static IP address configuration costs more than DHCP configuration.
Simplified configuration. Dynamic IP address assignment dramatically simplifies device configuration
Centralized management. You can modify the configuration for multiple subnets by simply modifying the DHCP
server configuration.
Address Pool
After a server receives a client's request packet, it chooses a valid address pool, determines an available IP address from
the pool through PING, and pushes the pool and address configuration to the client. The lease information is saved locally
for validity check upon lease renewal.
An address pool may carry various configuration parameters as follows:
An IP address range, which is the range of IP addresses that are available.
A gateway address. A maximum of 8 gateway addresses are supported.
A DNS address. A maximum of 8 DNS addresses are supported.
A lease period notifying clients of when to age an address and request a lease renewal.
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