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Default: DHCP service is disabled by default.
Command mode: Global Mode
Usage Guide: Both DHCP server and DHCP relay are included in the DHCP service.
When DHCP service enables, both DHCP server and DHCP relay are
enabled. ES4626/ES4650 can only assign IP address for the DHCP clients
and enable DHCP relay when DHCP server function is enabled.
Example: Enable DHCP server.
Switch(Config)#service dhcp
11.3 DHCP Relay Configuration
When the DHCP client and server are in different segments, DHCP relay is required to
transfer DHCP packets. Adding a DHCP relay makes it unnecessary to configure a DHCP
server for each segment, one DHCP server can provide the network configuration
parameter for clients from multiple segments, which is not only cost-effective but also
management-effective.
Fig 11-2 DHCP relay
As shown in the above figure, the DHCP client and the DHCP server are in different
networks, the DHCP client performs the four DHCP steps as usual yet DHCP relay is
added to the process.
1. The client broadcasts a DHCPDISCOVER packet, and DHCP relay inserts its
own IP address to the relay agent field in the DHCPDISCOVER packet on
receiving the packet, and forwards the packet to the specified DHCP server (for
DHCP frame format, please refer to RFC2131).
2. On the receiving the DHCPDISCOVER packets forwarded by DHCP relay, the
DHCP server sends the DHCPOFFER packet via DHCP relay to the DHCP client.
3. DHCP client chooses a DHCP server and broadcasts a DHCPREPLY packet,
DHCP relay forwards the packet to the DHCP server after processing.
4. On receiving DHCPREPLY, the DHCP server responds with a DHCPACK packet
via DHCP relay to the DHCP client.