ES4626-SFP Management Guide.pdf

configuration as well as various commands useful in network configuration to meet
different user needs. The definition of option code is described in detail in RFC2123.
Example: Setting the WWW server address as 10.1.128.240.
Switch(dhcp-1-config)#option 72 ip 10.1.128.240
11.2.2.19 service dhcp
Command: service dhcp
no service dhcp
Function: Enables DHCP server; the “no service dhcp” command disables the DHCP
service.
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 services are enabled, both DHCP server and DHCP relay are enabled.
ES4624-SFP/ES4626-SFP switch can only assign IP address for the DHCP clients and
enable DHCP relay when DHCP server function is enabled.
Example: Enabling 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.
DHCPDiscover(Broadcast)
DHCPDiscover
DHCPOFFER(Unicast)
DHCPOFFER
DHCPREQUEST(Broadcast)
DHCPREQUEST
DHCP Client
DHCPACK(Unicast)
DHCP Relay
DHCPACK
DHCP Server
Fig 10-2 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
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