Configuration Guide Configuring DHCPConfiguring DHCP
agent unicasts DHCP request packets to a DHCP server and forwards DHCP reply packets to a DCHP client. The DHCP
relay agent serves as a repeater connecting a DHCP client and a DHCP server of different network segments by
forwarding DHCP request packets and DHCP reply packets. The Client-Relay-Server mode achieves management of IP
addresses across multiple network segments by only one DHCP server. See the following figure.
Figure 4-8 DHCP Relay Scenario
VLAN 10 and VLAN 20 correspond to the segments 10.0.0.1/16 and 20.0.0.1/16 respectively. A DHCP server with IP
address 30.0.0.2 is in segment 30.0.0.1/16. To achieve management of dynamic IP addresses in VLAN 10 and VLAN 20
by the DHCP server, you only need to enable DHCP Relay on a gateway and configure IP address 30.0.0.2 for the DHCP
server.
 DHCP Relay Agent Information (Option 82)
As defined in RFC3046, an option can be added to indicate a DHCP client's network information when DHCP Relay is
performed, so that a DHCP server may assign IP addresses of various privileges based on more accurate information.
The option is called Option 82. Currently, Ruijie devices support schemes of relay agent information, which are described
as follows:
13. Relay agent information option82: This scheme serves without correlation with other protocol modules. A DHCP
relay agent forms an Option 82 based on the physical port receiving DHCP request packets and the MAC address of
the device. The option format is shown in the following figure.
Figure 4-9 Agent Circuit ID
Figure 4-10 Agent Remote ID
 DHCP Relay Check Server-ID
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