CLI Reference Guide-R05

Chapter 25 | DHCP Commands
DHCP Relay
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packet to a DHCP server on another network. When the server receives the
DHCP request, it allocates a free IP address for the DHCP client from its defined
scope for the DHCP client’s subnet, and sends a DHCP response back to the
DHCP relay agent (i.e., this switch). This switch then passes the DHCP response
received from the server to the client.
◆ You must specify the IP address for at least one active DHCP server. Otherwise,
the switch’s DHCP relay agent will not be able to forward client requests to a
DHCP server. Up to five DHCP servers can be specified in order of preference.
If any of the specified DHCP server addresses are not located in the same
network segment with this switch, use the ip default-gateway or ipv6 default-
gateway command to specify the default router through which this switch can
reach other IP subnetworks.
◆ To start DHCP relay service, enter the ip dhcp restart relay command.
Example
Console(config)#interface vlan 1
Console(config-if)#ip dhcp relay server 192.168.10.19
Console(config-if)#
Related Commands
ip dhcp restart relay (620)
ip dhcp restart relay This command enables DHCP relay for the specified VLAN. Use the no form to
disable it.
Default Setting
Disabled
Command Mode
Privileged Exec
Command Usage
This command is used to configure DHCP relay functions for host devices attached
to the switch. If DHCP relay service is enabled, and this switch sees a DHCP request
broadcast, it inserts its own IP address into the request so the DHCP server will
know the subnet where the client is located. Then, the switch forwards the packet
to the DHCP server on another network. When the server receives the DHCP
request, it allocates a free IP address for the DHCP client from its defined scope for
the DHCP client’s subnet, and sends a DHCP response back to the DHCP relay agent
(i.e., this switch). This switch then broadcasts the DHCP response received from the
server to the client.